Publications

@article{Pi2025,

title = {Levitation and controlled MHz rotation of a nanofabricated rod by a high-NA metalens},

author = {Hailong Pi and Chuang Sun and Kian Shen Kiang and Tiberius Georgescu and Bruce Jun-Yu Ou and Hendrik Ulbricht and Jize Yan},

doi = {10.1038/s41378-025-00886-7},

issn = {2055-7434},

year  = {2025},

date = {2025-12-00},

journal = {Microsyst Nanoeng},

volume = {11},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {Abstract

          An optically levitated nanoparticle in a vacuum provides an ideal platform for ultra-precision measurements and fundamental physics studies because of the exceptionally high-quality factor and rich motion modes, which can be engineered by manipulating the optical field and the geometry of the nanoparticle. Nanofabrication technology with the ability to create arbitrary nanostructure arrays offers a precise way of engineering the optical field and the geometry of the nanoparticle. Here, for the first time, we optically levitate and rotate a nanofabricated nanorod via a nanofabricated a-Si metalens which strongly focuses a 1550 nm laser beam with a numerical aperture of 0.953. By manipulating the laser beam’s polarization, the levitated nanorod’s translation frequencies can be tuned, and the spin rotation mode can be switched on and off. Then, we showed the control of rotational frequency by changing the laser beam’s intensity and polarization as well as the air pressure. Finally, a MHz spin rotation frequency of the nanorod is achieved in the experiment. This is the first demonstration of controlled optical spin in a metalens-based compact optical levitation system. Our research holds promise for realizing scalable on-chip integrated optical levitation systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Homans2025,

title = {An experimental platform for levitated mechanics in space},

author = {Jack Homans and Elliot Simcox and Jakub Wardak and Laura da Palma Barbara and Tim M Fuchs and Rafael Mufato and Florence Concepcion and Andrei Dragomir and Christian Vogt and Peter Nisbet-Jones and Christopher Bridges and Hendrik Ulbricht},

doi = {10.1088/2058-9565/ade624},

issn = {2058-9565},

year  = {2025},

date = {2025-10-01},

journal = {Quantum Sci. Technol.},

volume = {10},

number = {3},

publisher = {IOP Publishing},

abstract = {Abstract

               Conducting experiments in extreme conditions has long been the aim of the levitated mechanics field, as it allows for the investigation of new fundamental physics phenomena. Sending these experiments into the micro-g environment of space has been one such milestone, with multiple proposals calling for such a platform. At the same time, levitated sensors have demonstrated a high sensitivity to external stimuli, such as electric, magnetic and gravitational forces, which will only improve in low-vibrational conditions. This paper describes the development of a technology demonstrator for optical and magnetic trapping experiments in space. Our payload represents the first concrete step towards future missions with aims of probing fundamental physical questions: matter-wave interferometry of nanoparticles to probe the limits of macroscopic quantum mechanics, detection of Dark Matter candidates and gravitational waves to test physics beyond the Standard Model, and accelerometry for Earth-observation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gundhi2025,

title = {Measuring Decoherence Due to Quantum Vacuum Fluctuations},

author = {Anirudh Gundhi and Hendrik Ulbricht},

doi = {10.1103/s5c9-zjt9},

issn = {1079-7114},

year  = {2025},

date = {2025-07-00},

journal = {Phys. Rev. Lett.},

volume = {135},

number = {2},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Amaral2025,

title = {First Search for Ultralight Dark Matter Using a Magnetically Levitated Particle},

author = {Dorian W. P. Amaral and Dennis G. Uitenbroek and Tjerk H. Oosterkamp and Christopher D. Tunnell},

doi = {10.1103/physrevlett.134.251001},

issn = {1079-7114},

year  = {2025},

date = {2025-06-00},

journal = {Phys. Rev. Lett.},

volume = {134},

number = {25},

publisher = {American Physical Society (APS)},

abstract = {We perform the first search for ultralight dark matter using a magnetically levitated particle. A submillimeter permanent magnet is levitated in a superconducting trap with a measured force sensitivity of 0.2  fN/Hz. We find no evidence of a signal and derive limits on dark matter coupled to the difference between baryon and lepton number, B−L, in the mass range (1.10360−1.10485)×10−13  eV/c2. Our most stringent limit on the coupling strength is gB−L≲2.98×10−21. We propose the POLONAISE (Probing Oscillations using Levitated Objects for Novel Accelerometry In Searches of Exotic physics) experiment, which features short-, medium-, and long-term upgrades that will give us leading sensitivity in a wide mass range, demonstrating the promise of this novel quantum sensing technology in the hunt for dark matter.

          

            

            

              

                Published by the American Physical Society

                2025

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pfeifer2025,

title = {Gravitational attraction of ultrarelativistic matter: A new testbed for modified gravity at the Large Hadron Collider},

author = {Christian Pfeifer and Dennis Rätzel and Daniel Braun},

doi = {10.1103/physrevd.111.084073},

issn = {2470-0029},

year  = {2025},

date = {2025-04-00},

journal = {Phys. Rev. D},

volume = {111},

number = {8},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ahrens2025,

title = {Levitated Ferromagnetic Magnetometer with Energy Resolution Well Below 

ℏ},

author = {Felix Ahrens and Wei Ji and Dmitry Budker and Chris Timberlake and Hendrik Ulbricht and Andrea Vinante},

doi = {10.1103/physrevlett.134.110801},

issn = {1079-7114},

year  = {2025},

date = {2025-03-00},

journal = {Phys. Rev. Lett.},

volume = {134},

number = {11},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Muffato2025,

title = {Generation of classical non-Gaussian states by squeezing a thermal state into nonlinear motion of levitated optomechanics},

author = {R. Muffato and T. S. Georgescu and J. Homans and T. Guerreiro and Q. Wu and D. A. Chisholm and M. Carlesso and M. Paternostro and H. Ulbricht},

doi = {10.1103/physrevresearch.7.013171},

issn = {2643-1564},

year  = {2025},

date = {2025-02-00},

journal = {Phys. Rev. Research},

volume = {7},

number = {1},

publisher = {American Physical Society (APS)},

abstract = {We report on an experiment achieving the dynamical generation of non-Gaussian states of motion of a levitated optomechanical system. We access intrinsic Duffing-like nonlinearities by thermal squeezing of an oscillator's state of motion by rapidly switching the frequency of its trap. We characterize the experimental non-Gaussian state versus expectations from simulations and give prospects for the emergence of genuine nonclassical features.

          

            

            

              

                Published by the American Physical Society

                2025

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Altamura2025,

title = {Improved bounds on collapse models from rotational noise of the Laser Interferometer Space Antenna Pathfinder mission},

author = {Davide Giordano Ario Altamura and Andrea Vinante and Matteo Carlesso},

doi = {10.1103/physreva.111.l020203},

issn = {2469-9934},

year  = {2025},

date = {2025-02-00},

journal = {Phys. Rev. A},

volume = {111},

number = {2},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bose2025,

title = {Massive quantum systems as interfaces of quantum mechanics and gravity},

author = {Sougato Bose and Ivette Fuentes and Andrew A. Geraci and Saba Mehsar Khan and Sofia Qvarfort and Markus Rademacher and Muddassar Rashid and Marko Toroš and Hendrik Ulbricht and Clara C. Wanjura},

doi = {10.1103/revmodphys.97.015003},

issn = {1539-0756},

year  = {2025},

date = {2025-02-00},

journal = {Rev. Mod. Phys.},

volume = {97},

number = {1},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Crognaletti2024,

title = {Equivariant Variational Quantum Eigensolver to detect phase transitions through energy level crossings},

author = {Giulio Crognaletti and Giovanni Di Bartolomeo and Michele Vischi and Luciano Loris Viteritti},

doi = {10.1088/2058-9565/ad9be3},

issn = {2058-9565},

year  = {2025},

date = {2025-01-01},

journal = {Quantum Sci. Technol.},

volume = {10},

number = {1},

publisher = {IOP Publishing},

abstract = {Abstract

               Level spectroscopy stands as a powerful method for identifying the transition point that delineates distinct quantum phases. Since each quantum phase exhibits a characteristic sequence of excited states, the crossing of energy levels between low-lying excited states offers a reliable mean to estimate the phase transition point. While approaches like the Variational Quantum Eigensolver are useful for approximating ground states of interacting systems using quantum computing, capturing low-energy excitations remains challenging. In our study, we introduce an equivariant quantum circuit that preserves the total spin and the translational symmetry to accurately describe singlet and triplet excited states in the J

                  1–J

                  2 Heisenberg model on a chain, which are crucial for characterizing its transition point. Additionally, we assess the impact of noise on the variational state, showing that conventional mitigation techniques like Zero Noise Extrapolation reliably restore its physical properties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sgroi2024,

title = {Efficient excitation-transfer across fully connected networks via local-energy optimization},

author = {S. Sgroi and G. Zicari and A. Imparato and M. Paternostro},

doi = {10.1140/epjqt/s40507-024-00238-w},

issn = {2196-0763},

year  = {2024},

date = {2024-12-00},

journal = {EPJ Quantum Technol.},

volume = {11},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractWe study the excitation transfer across a fully connected quantum network whose sites energies can be artificially designed. Starting from a simplified model of a broadly-studied physical system, we systematically optimize its local energies to achieve high excitation transfer for various environmental conditions, using an adaptive Gradient Descent technique and Automatic Differentiation. We show that almost perfect transfer can be achieved with and without local dephasing, provided that the dephasing rates are not too large. We investigate our solutions in terms of resilience against variations in either the network connection strengths, or size, as well as coherence losses. We highlight the different features of a dephasing-free and dephasing-driven transfer. Our work gives further insight into the interplay between coherence and dephasing effects in excitation-transfer phenomena across fully connected quantum networks. In turn, this will help designing optimal transfer in artificial open networks through the simple manipulation of local energies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Braidotti2024,

title = {Amplification of electromagnetic fields by a rotating body},

author = {M. C. Braidotti and A. Vinante and M. Cromb and A. Sandakumar and D. Faccio and H. Ulbricht},

doi = {10.1038/s41467-024-49689-w},

issn = {2041-1723},

year  = {2024},

date = {2024-12-00},

journal = {Nat Commun},

volume = {15},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractIn 1971, Zel’dovich predicted the amplification of electromagnetic (EM) waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body. This phenomenon was believed to be unobservable with electromagnetic fields due to technological difficulties in meeting the condition of amplification that is, the cylinder must rotate faster than the frequency of the incoming radiation. Here, we measure the amplification of an electromagnetic field, generated by a toroid LC-circuit, scattered by an aluminium cylinder spinning in the toroid gap. We show that when the Zel’dovich condition is met, the resistance induced by the cylinder becomes negative implying amplification of the incoming EM fields. These results reveal the connection between the concept of induction generators and the physics of this fundamental physics effect and open new prospects towards testing the Zel’dovich mechanism in the quantum regime, as well as related quantum friction effects.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gundhi2024,

title = {Decoherence due to the Casimir effect?},

author = {Anirudh Gundhi},

doi = {10.1103/physrevd.110.116001},

issn = {2470-0029},

year  = {2024},

date = {2024-12-00},

journal = {Phys. Rev. D},

volume = {110},

number = {11},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DiBartolomeo2024b,

title = {Efficient quantum algorithm to simulate open systems through a single environmental qubit},

author = {Giovanni Di Bartolomeo and Michele Vischi and Tommaso Feri and Angelo Bassi and Sandro Donadi},

doi = {10.1103/physrevresearch.6.043321},

issn = {2643-1564},

year  = {2024},

date = {2024-12-00},

journal = {Phys. Rev. Research},

volume = {6},

number = {4},

publisher = {American Physical Society (APS)},

abstract = {We present an efficient algorithm for simulating open quantum systems dynamics described by the Lindblad master equation on quantum computers, addressing key challenges in the field. In contrast to existing approaches, our method achieves two significant advancements. First, we employ a repetition of unitary gates on a set of n system qubits and, remarkably, only a single ancillary bath qubit representing the environment. It follows that, for the typical case of m locality of the Lindblad operators, we reach an exponential improvement of the number of ancilla in terms of m and up to a polynomial improvement in ancilla overhead for large n with respect to other approaches. Although stochasticity is introduced, requiring multiple circuit realizations, the sampling overhead is independent of the system size. Second, we show that, under fixed accuracy conditions, our algorithm enables a reduction in the number of Trotter steps compared to other approaches, substantially decreasing circuit depth. These advancements hold particular significance for near-term quantum computers, where minimizing both width and depth is critical due to inherent noise in their dynamics.

          

            

            

              

                Published by the American Physical Society

                2024

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hernández-Gómez2024,

title = {Interferometry of quantum correlation functions to access quasiprobability distribution of work},

author = {Santiago Hernández-Gómez and Takuya Isogawa and Alessio Belenchia and Amikam Levy and Nicole Fabbri and Stefano Gherardini and Paola Cappellaro},

doi = {10.1038/s41534-024-00913-x},

issn = {2056-6387},

year  = {2024},

date = {2024-12-00},

journal = {npj Quantum Inf},

volume = {10},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractThe Kirkwood-Dirac quasiprobability distribution, intimately connected with the quantum correlation function of two observables measured at distinct times, is becoming increasingly relevant for fundamental physics and quantum technologies. This quasiprobability distribution can take non-positive values, and its experimental reconstruction becomes challenging when expectation values of incompatible observables are involved. Here, we use an interferometric scheme aided by an auxiliary system to reconstruct the Kirkwood-Dirac quasiprobability distribution. We experimentally demonstrate this scheme in an electron-nuclear spin system associated with a nitrogen-vacancy center in diamond. By measuring the characteristic function, we reconstruct the quasiprobability distribution of work and analyze the behavior of its first and second moments. Our results clarify the physical meaning of the work quasiprobability distribution in the context of quantum thermodynamics. Finally, we study the uncertainty of measuring the Hamiltonian of the system at two times, via the Robertson-Schrödinger uncertainty relation, for different initial states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lenler-Eriksen2024,

title = {Testing continuous spontaneous localization model with charged macromolecules},

author = {Emil Lenler-Eriksen and Michael Drewsen and Matteo Carlesso},

doi = {10.1088/1367-2630/ad904a},

issn = {1367-2630},

year  = {2024},

date = {2024-11-01},

journal = {New J. Phys.},

volume = {26},

number = {11},

publisher = {IOP Publishing},

abstract = {Abstract

               In the last decade, a growing interest has been devoted to models of spontaneous collapse of the wavefunction, known also as collapse models. They coherently solve the well-known quantum measurement problem by suitably modifying the Schrödinger evolution. Quantum experiments are now finally within the reach of testing such models (and thus testing the limits of quantum theory). Here, we propose a method based on a two-ions confined in a linear Paul trap to possibly enhance the testing capabilities of such experiments. The combination of an atomic and a macromolecular ion provide a good match for the cooling of the motional degrees of freedom and a non-negligible insight in the collapse mechanism, respectively.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Figurato2024c,

title = {On the effectiveness of the collapse in the Diósi–Penrose model},

author = {Laria Figurato and Marco Dirindin and José Luis Gaona-Reyes and Matteo Carlesso and Angelo Bassi and Sandro Donadi},

doi = {10.1088/1367-2630/ad8c77},

issn = {1367-2630},

year  = {2024},

date = {2024-11-01},

journal = {New J. Phys.},

volume = {26},

number = {11},

publisher = {IOP Publishing},

abstract = {Abstract

               The possibility that gravity plays a role in the collapse of the quantum wave function has been considered in the literature, and it is of relevance not only because it would provide a solution to the measurement problem in quantum theory, but also because it would give a new and unexpected twist to the search for a unified theory of quantum and gravitational phenomena, possibly overcoming the current impasse. The Diósi–Penrose model is the most popular incarnation of this idea. It predicts a progressive breakdown of quantum superpositions when the mass of the system increases; as such, it is susceptible to experimental verification. Current experiments set a lower bound 

                     

                     

                        

                           

                              R

                              0

                           

                           ≳

                           4

                        

                     

                   Å  for the free parameter of the model, excluding some versions of it. In this work we search for an upper bound, coming from the request that the collapse is effective enough to guarantee classicality at the macroscopic scale: we find out that not all macroscopic systems collapse effectively. If one relaxes this request, a reasonable (although to some degree arbitrary) bound is found to be: 

                     

                     

                        

                           

                              R

                              0

                           

                           ≲

                           

                              10

                              6

                           

                        

                     

                   Å. This will serve to better direct future experiments to further test the model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ciszak2024,

title = {Quantum gravity inspired nonlocal quantum dynamics preserving the classical limit},

author = {Marzena Ciszak and Alessio Belenchia and Antonello Ortolan and Francesco Marino},

doi = {10.1088/1361-6382/ad7774},

issn = {1361-6382},

year  = {2024},

date = {2024-10-17},

journal = {Class. Quantum Grav.},

volume = {41},

number = {20},

publisher = {IOP Publishing},

abstract = {Abstract

               Several approaches to quantum gravity lead to nonlocal modifications of fields’ dynamics. This, in turn, can give rise to nonlocal modifications of quantum mechanics at non-relativistic energies. Here, we analyze the nonlocal Schrödinger evolution of a quantum harmonic oscillator in one such scenario, where the problem can be addressed without the use of perturbation theory. We demonstrate that although deviations from standard quantum predictions occur at low occupation numbers, where they could potentially be detected or constrained by high-precision experiments, the classical limits of quantum probability densities and free energy remain unaffected up to energies comparable with the nonlocality scale. These results provide an example of nonlocal quantum dynamics compatible with classical predictions, suggesting massive quantum objects as a promising avenue for testing some phenomenological aspects of quantum gravity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hanif2024,

title = {Testing Whether Gravity Acts as a Quantum Entity When Measured},

author = {Farhan Hanif and Debarshi Das and Jonathan Halliwell and Dipankar Home and Anupam Mazumdar and Hendrik Ulbricht and Sougato Bose},

doi = {10.1103/physrevlett.133.180201},

issn = {1079-7114},

year  = {2024},

date = {2024-10-00},

journal = {Phys. Rev. Lett.},

volume = {133},

number = {18},

publisher = {American Physical Society (APS)},

abstract = {A defining signature of classical systems is “in principle measurability” without disturbance: a feature manifestly violated by quantum systems. We describe a multi-interferometer experimental setup that can, in principle, reveal the nonclassicality of a spatial superposition-sourced gravitational field if an irreducible disturbance is caused by a measurement of gravity. While one interferometer sources the field, the others are used to measure the gravitational field created by the superposition. This requires neither any specific form of nonclassical gravity, nor the generation of entanglement between any relevant degrees of freedom at any stage, thus distinguishing it from the experiments proposed so far. This test, when added to the recent entanglement-witness based proposals, enlarges the domain of quantum postulates being tested for gravity. Moreover, the proposed test yields a signature of quantum measurement induced disturbance for any finite rate of decoherence, and is device independent.

          

            

            

              

                Published by the American Physical Society

                2024

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Vischi2024,

title = {Simulating photonic devices with noisy optical elements},

author = {Michele Vischi and Giovanni Di Bartolomeo and Massimiliano Proietti and Seid Koudia and Filippo Cerocchi and Massimiliano Dispenza and Angelo Bassi},

doi = {10.1103/physrevresearch.6.033337},

issn = {2643-1564},

year  = {2024},

date = {2024-09-00},

journal = {Phys. Rev. Research},

volume = {6},

number = {3},

publisher = {American Physical Society (APS)},

abstract = {Quantum computers are inherently affected by noise. While in the long term, error correction codes will account for noise at the cost of increasing physical qubits, in the near term, the performance of any quantum algorithm should be tested and simulated in the presence of noise. As noise acts on the hardware, the classical simulation of a quantum algorithm should not be agnostic on the platform used for the computation. In this paper, we apply the recently proposed noisy gates approach to efficiently simulate noisy optical circuits described in the dual rail framework. The evolution of the state vector is simulated directly, without requiring the mapping to the density matrix framework. Notably, we test the method on both the gate-based and measurement-based quantum computing models, showing that the approach is very versatile. We also evaluate the performance of a photonic variational quantum algorithm to solve the MAX-2-CUT problem. In particular we design and simulate an ansatz, which is resilient to photon losses up to p∼10−3 making it relevant for near-term applications.

          

            

            

              

                Published by the American Physical Society

                2024

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Timberlake2024,

title = {Linear cooling of a levitated micromagnetic cylinder by vibration},

author = {Chris Timberlake and Elliot Simcox and Hendrik Ulbricht},

doi = {10.1103/physrevresearch.6.033345},

issn = {2643-1564},

year  = {2024},

date = {2024-09-00},

journal = {Phys. Rev. Research},

volume = {6},

number = {3},

publisher = {American Physical Society (APS)},

abstract = {We report feedback cooling of translational and librational degrees of freedom of a levitated m icromagnet cylinder, utilizing a piezoelectric actuator to apply linear feedback to high-Q mechanical modes. The normal modes are measured with a superconducting pick-up coil coupled to a dc SQUID, and phase information is fed back to the piezoelectric actuator to feedback cool a center-of-mass mode to ∼7K, and a librational mode to 830±200mK. Q-factors of 1.0×107 are evaluated for the center-of-mass mode. We find that it is plausible to achieve ground state cooling of the center-of-mass mode by introducing vibration isolation, optimizing the geometry of the pick-up coil to focus on the specific mode of interest and utilizing a state-of-the-art SQUID for detection.

          

            

            

              

                Published by the American Physical Society

                2024

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2024,

title = {Squeezing below the ground state of motion of a continuously monitored levitating nanoparticle},

author = {Qiongyuan Wu and Diana A Chisholm and Rafael Muffato and Tiberius Georgescu and Jack Homans and Hendrik Ulbricht and Matteo Carlesso and Mauro Paternostro},

doi = {10.1088/2058-9565/ad7284},

issn = {2058-9565},

year  = {2024},

date = {2024-08-22},

journal = {Quantum Sci. Technol.},

publisher = {IOP Publishing},

abstract = {Abstract

               Squeezing is a crucial resource for quantum information processing and quantum sensing. In levitated nanomechanics, squeezed states of motion can be generated via temporal control of the trapping frequency of a massive particle. However, the amount of achievable squeezing typically suffers from detrimental environmental effects. We analyze the performance of a scheme that, by embedding careful time-control of trapping potentials and fully accounting for the most relevant sources of noise – including measurement backaction – achieves significant levels of mechanical squeezing. The feasibility of our proposal, which is close to experimental state-of-the-art, makes it a valuable tool for quantum state engineering.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Belenchia2024,

title = {Non-linear media in weakly curved spacetime: optical solitons and probe pulses for gravimetry},

author = {Alessio Belenchia and Felix Spengler and Dennis Rätzel and Daniel Braun},

doi = {10.1088/1367-2630/ad678d},

issn = {1367-2630},

year  = {2024},

date = {2024-08-01},

journal = {New J. Phys.},

volume = {26},

number = {8},

publisher = {IOP Publishing},

abstract = {Abstract

               That light propagating in a gravitational field gets frequency-shifted is one of the basic consequences of any metric theory of gravity rooted in the equivalence principle. At the same time, also a time dependent material’s refractive index can frequency-shift light propagating in it. The mathematical analogy between the two effects is such that the latter has been used to study the optical analogue of a black-hole spacetime. Here, we combine these two effects by showing that light propagation in non-linear media in the presence of a moving refractive index perturbation can lead to a gravity-dependent blueshift. We find that the predicted blueshift surpasses the gravitational redshift even if the medium is considered to be perfectly stiff. In realistic scenarios, by far the strongest frequency shift arises due to the deformation of the dielectric medium and the corresponding photoelastic change of refractive index. This has the potential to facilitate optical sensing of small gravity gradients.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Janse2024,

title = {Current experimental upper bounds on spacetime diffusion},

author = {Martijn Janse and Dennis G. Uitenbroek and Loek van Everdingen and Jaimy Plugge and Bas Hensen and Tjerk H. Oosterkamp},

doi = {10.1103/physrevresearch.6.033076},

issn = {2643-1564},

year  = {2024},

date = {2024-07-00},

journal = {Phys. Rev. Research},

volume = {6},

number = {3},

publisher = {American Physical Society (APS)},

abstract = {A theory describing the dynamics of quantum systems interacting on a classical spacetime was recently put forward by Oppenheim  Quantum states may retain their coherence, at the cost of some amount of stochasticity of the spacetime metric, characterized by a spacetime diffusion parameter. Here, we report existing experimental upper bounds on such spacetime diffusion, based on a review of several types of experiments with very low force noise over a broad range of test masses from single atoms to several kilograms. We find an upper bound at least 15 orders of magnitude lower as compared to the initial bounds for explicit models presented by Oppenheim . The results presented here provide a path forward for future experiments that can help evaluate classical-quantum theories.

          

            

            

              

                Published by the American Physical Society

                2024

              

            

          },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Altamura2024,

title = {Noninterferometric rotational test of the continuous spontaneous localization model: Enhancement of the collapse noise through shape optimization},

author = {Davide Giordano Ario Altamura and Matteo Carlesso and Sandro Donadi and Angelo Bassi},

doi = {10.1103/physreva.109.062212},

issn = {2469-9934},

year  = {2024},

date = {2024-06-00},

journal = {Phys. Rev. A},

volume = {109},

number = {6},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Piscicchia2024,

title = {X-Ray Emission from Atomic Systems Can Distinguish between Prevailing Dynamical Wave-Function Collapse Models},

author = {Kristian Piscicchia and Sandro Donadi and Simone Manti and Angelo Bassi and Maaneli Derakhshani and Lajos Diósi and Catalina Curceanu},

doi = {10.1103/physrevlett.132.250203},

issn = {1079-7114},

year  = {2024},

date = {2024-06-00},

journal = {Phys. Rev. Lett.},

volume = {132},

number = {25},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DiBartolomeo2024,

title = {Experimental bounds on linear-friction dissipative collapse models from levitated optomechanics},

author = {Giovanni Di Bartolomeo and Matteo Carlesso},

doi = {10.1088/1367-2630/ad3842},

issn = {1367-2630},

year  = {2024},

date = {2024-04-01},

journal = {New J. Phys.},

volume = {26},

number = {4},

publisher = {IOP Publishing},

abstract = {Abstract

               Collapse models constitute an alternative to quantum mechanics that solve the well-know quantum measurement problem. In this framework, a novel approach to include dissipation in collapse models has been recently proposed, and awaits experimental scrutiny. Our work establishes experimental bounds on the so-constructed linear-friction dissipative Diósi-Penrose (dDP) and Continuous Spontaneous localisation (dCSL) models by exploiting experiments in the field of levitated optomechanics. Our results in the dDP case exclude collapse temperatures below 10−13 K and 

                     

                     

                        

                           6

                           ×

                           

                              10

                              

                                 −

                                 12

                              

                           

                        

                     

                     

                   K respectively for values of the localisation length smaller than 10−6 m and 10−8 m. In the dCSL case the entire parameter space is excluded for values of the temperature lower than 

                     

                     

                        

                           6

                           ×

                           

                              10

                              

                                 −

                                 9

                              

                           

                        

                     

                     

                   K.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Suprano2024,

title = {Experimental Property Reconstruction in a Photonic Quantum Extreme Learning Machine},

author = {Alessia Suprano and Danilo Zia and Luca Innocenti and Salvatore Lorenzo and Valeria Cimini and Taira Giordani and Ivan Palmisano and Emanuele Polino and Nicolò Spagnolo and Fabio Sciarrino and G. Massimo Palma and Alessandro Ferraro and Mauro Paternostro},

doi = {10.1103/physrevlett.132.160802},

issn = {1079-7114},

year  = {2024},

date = {2024-04-00},

journal = {Phys. Rev. Lett.},

volume = {132},

number = {16},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Barr2024,

title = {Spectral density classification for environment spectroscopy},

author = {J Barr and G Zicari and A Ferraro and M Paternostro},

doi = {10.1088/2632-2153/ad2cf1},

issn = {2632-2153},

year  = {2024},

date = {2024-03-01},

journal = {Mach. Learn.: Sci. Technol.},

volume = {5},

number = {1},

publisher = {IOP Publishing},

abstract = {Abstract

               Spectral densities encode the relevant information characterizing the system–environment interaction in an open-quantum system problem. Such information is key to determining the system’s dynamics. In this work, we leverage the potential of machine learning techniques to reconstruct the features of the environment. Specifically, we show that the time evolution of a system observable can be used by an artificial neural network to infer the main features of the spectral density. In particular, for relevant examples of spin-boson models, we can classify with high accuracy the Ohmicity parameter of the environment as either Ohmic, sub-Ohmic or super-Ohmic, thereby distinguishing between different forms of dissipation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fuchs2024,

title = {Measuring gravity with milligram levitated masses},

author = {Tim M. Fuchs and Dennis G. Uitenbroek and Jaimy Plugge and Noud van Halteren and Jean-Paul van Soest and Andrea Vinante and Hendrik Ulbricht and Tjerk H. Oosterkamp},

doi = {10.1126/sciadv.adk2949},

issn = {2375-2548},

year  = {2024},

date = {2024-02-23},

journal = {Sci. Adv.},

volume = {10},

number = {8},

publisher = {American Association for the Advancement of Science (AAAS)},

abstract = {Gravity differs from all other known fundamental forces because it is best described as a curvature of space-time. For that reason, it remains resistant to unifications with quantum theory. Gravitational interaction is fundamentally weak and becomes prominent only at macroscopic scales. This means, we do not know what happens to gravity in the microscopic regime where quantum effects dominate and whether quantum coherent effects of gravity become apparent. Levitated mechanical systems of mesoscopic size offer a probe of gravity, while still allowing quantum control over their motional state. This regime opens the possibility of table-top testing of quantum superposition and entanglement in gravitating systems. Here, we show gravitational coupling between a levitated submillimeter-scale magnetic particle inside a type I superconducting trap and kilogram source masses, placed approximately half a meter away. Our results extend gravity measurements to low gravitational forces of attonewton and underline the importance of levitated mechanical sensors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gaona-Reyes2024,

title = {Spontaneous collapse models lead to the emergence of classicality of the Universe},

author = {José Luis Gaona-Reyes and Lucía Menéndez-Pidal and Mir Faizal and Matteo Carlesso},

doi = {10.1007/jhep02(2024)193},

issn = {1029-8479},

year  = {2024},

date = {2024-02-00},

journal = {J. High Energ. Phys.},

volume = {2024},

number = {2},

publisher = {Springer Science and Business Media LLC},

abstract = {Abstract

                     Assuming that Quantum Mechanics is universal and that it can be applied over all scales, then the Universe is allowed to be in a quantum superposition of states, where each of them can correspond to a different space-time geometry. How can one then describe the emergence of the classical, well-defined geometry that we observe? Considering that the decoherence-driven quantum-to-classical transition relies on external physical entities, this process cannot account for the emergence of the classical behaviour of the Universe. Here, we show how models of spontaneous collapse of the wavefunction can offer a viable mechanism for explaining such an emergence. We apply it to a simple General Relativity dynamical model for gravity and a perfect fluid. We show that, by starting from a general quantum superposition of different geometries, the collapse dynamics leads to a single geometry, thus providing a possible mechanism for the quantum-to-classical transition of the Universe. Similarly, when applying our dynamics to the physically-equivalent Parametrised Unimodular gravity model, we obtain a collapse on the basis of the cosmological constant, where eventually one precise value is selected, thus providing also a viable explanation for the cosmological constant problem. Our formalism can be easily applied to other quantum cosmological models where we can choose a well-defined clock variable.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wardak2024,

title = {Nanoparticle Interferometer by Throw and Catch},

author = {Jakub Wardak and Tiberius Georgescu and Giulio Gasbarri and Alessio Belenchia and Hendrik Ulbricht},

doi = {10.3390/atoms12020007},

issn = {2218-2004},

year  = {2024},

date = {2024-02-00},

journal = {Atoms},

volume = {12},

number = {2},

publisher = {MDPI AG},

abstract = {Matter wave interferometry with increasingly larger masses could pave the way to understanding the nature of wavefunction collapse, the quantum to classical transition, or even how an object in a spatial superposition interacts with its gravitational field. In order to improve upon the current mass record, it is necessary to move into the nanoparticle regime. In this paper, we provide a design for a nanoparticle Talbot–Lau matter wave interferometer that circumvents the practical challenges of previously proposed designs. We present numerical estimates of the expected fringe patterns that such an interferometer would produce, considering all major sources of decoherence. We discuss the practical challenges involved in building such an experiment, as well as some preliminary experimental results to illustrate the proposed measurement scheme. We show that such a design is suitable for seeing interference fringes with 106 amu SiO2 particles and that this design can be extended to even 108 amu particles by using flight times below the typical Talbot time of the system.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blair2024,

title = {Nonequilibrium quantum probing through linear response},

author = {S. Blair and G. Zicari and A. Belenchia and A. Ferraro and M. Paternostro},

doi = {10.1103/physrevresearch.6.013152},

issn = {2643-1564},

year  = {2024},

date = {2024-02-00},

journal = {Phys. Rev. Research},

volume = {6},

number = {1},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Figurato2024,

title = {On the testability of the Károlyházy model},

author = {Laria Figurato and Angelo Bassi and Sandro Donadi},

doi = {10.1088/1367-2630/ad1499},

issn = {1367-2630},

year  = {2024},

date = {2024-01-01},

journal = {New J. Phys.},

volume = {26},

number = {1},

publisher = {IOP Publishing},

abstract = {Abstract

               Károlyházy’s original proposal, suggesting that space-time fluctuations could be a source of decoherence in space, faced a significant challenge due to an unexpectedly high emission of radiation (13 orders of magnitude more than what was observed in the latest experiment). To address this issue, we reevaluated Károlyházy’s assumption that the stochastic metric fluctuation must adhere to a wave equation. By considering more general correlation functions of space-time fluctuations, we resolve the problem and consequently revive the aforementioned proposal.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Das2024,

title = {Mass-Independent Scheme to Test the Quantumness of a Massive Object},

author = {Debarshi Das and Dipankar Home and Hendrik Ulbricht and Sougato Bose},

doi = {10.1103/physrevlett.132.030202},

issn = {1079-7114},

year  = {2024},

date = {2024-01-00},

journal = {Phys. Rev. Lett.},

volume = {132},

number = {3},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hernández-Gómez2023,

title = {Experimental signature of initial quantum coherence on entropy production},

author = {Santiago Hernández-Gómez and Stefano Gherardini and Alessio Belenchia and Andrea Trombettoni and Mauro Paternostro and Nicole Fabbri},

doi = {10.1038/s41534-023-00738-0},

issn = {2056-6387},

year  = {2023},

date = {2023-12-00},

journal = {npj Quantum Inf},

volume = {9},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractWe report on the experimental quantification of the contribution to non-equilibrium entropy production stemming from the quantum coherence content in the initial state of a qubit exposed to both coherent driving and dissipation. Our experimental demonstration builds on the exquisite experimental control of the spin state of a nitrogen-vacancy defect in diamond and is underpinned, theoretically, by the formulation of a generalized fluctuation theorem designed to track the effects of quantum coherence. Our results provide significant evidence of the possibility to pinpoint the genuinely quantum mechanical contributions to the thermodynamics of non-equilibrium quantum processes in an open quantum systems scenario.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Innocenti2023,

title = {Potential and limitations of quantum extreme learning machines},

author = {L. Innocenti and S. Lorenzo and I. Palmisano and A. Ferraro and M. Paternostro and G. M. Palma},

doi = {10.1038/s42005-023-01233-w},

issn = {2399-3650},

year  = {2023},

date = {2023-12-00},

journal = {Commun Phys},

volume = {6},

number = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {AbstractQuantum extreme learning machines (QELMs) aim to efficiently post-process the outcome of fixed — generally uncalibrated — quantum devices to solve tasks such as the estimation of the properties of quantum states. The characterisation of their potential and limitations, which is currently lacking, will enable the full deployment of such approaches to problems of system identification, device performance optimization, and state or process reconstruction. We present a framework to model QELMs, showing that they can be concisely described via single effective measurements, and provide an explicit characterisation of the information exactly retrievable with such protocols. We furthermore find a close analogy between the training process of QELMs and that of reconstructing the effective measurement characterising the given device. Our analysis paves the way to a more thorough understanding of the capabilities and limitations of QELMs, and has the potential to become a powerful measurement paradigm for quantum state estimation that is more resilient to noise and imperfections.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DiBartolomeo2023b,

title = {Noisy gates for simulating quantum computers},

author = {Giovanni Di Bartolomeo and Michele Vischi and Francesco Cesa and Roman Wixinger and Michele Grossi and Sandro Donadi and Angelo Bassi},

doi = {10.1103/physrevresearch.5.043210},

issn = {2643-1564},

year  = {2023},

date = {2023-12-00},

journal = {Phys. Rev. Research},

volume = {5},

number = {4},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gianani2023,

title = {Diagnostics of quantum-gate coherences deteriorated by unitary errors via end-point-measurement statistics},

author = {Ilaria Gianani and Alessio Belenchia and Stefano Gherardini and Vincenzo Berardi and Marco Barbieri and Mauro Paternostro},

doi = {10.1088/2058-9565/acedca},

issn = {2058-9565},

year  = {2023},

date = {2023-10-01},

journal = {Quantum Sci. Technol.},

volume = {8},

number = {4},

publisher = {IOP Publishing},

abstract = {Abstract

               Quantum coherence is a central ingredient in quantum physics with several theoretical and technological ramifications. We consider a figure of merit encoding the information on how the coherence generated on average by a quantum gate is affected by unitary errors (coherent noise sources) in the form of rotation-angle and rotation-axis errors. We provide numerical evidences that such information is well captured by the statistics of local energy measurements on the output states of the gate. These findings are then corroborated by experimental data taken in a quantum optics setting.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Chisholm2023,

title = {The meaning of redundancy and consensus in quantum objectivity},

author = {Diana A. Chisholm and Luca Innocenti and G. Massimo Palma},

doi = {10.22331/q-2023-08-03-1074},

issn = {2521-327X},

year  = {2023},

date = {2023-08-03},

journal = {Quantum},

volume = {7},

publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},

abstract = {While the terms "redundancy" and "consensus" are often used as synonyms in the context of quantum objectivity, we show here that these should be understood as two related but distinct notions, that quantify different features of the quantum-to-classical transition. We show that the two main frameworks used to measure quantum objectivity, namely spectrum broadcast structure and quantum Darwinism, are best suited to quantify redundancy and consensus, respectively. Furthermore, by analyzing explicit examples of states with nonlocally encoded information, we highlight the potentially stark difference between the degrees of redundancy and consensus. In particular, this causes a break in the hierarchical relations between spectrum broadcast structure and quantum Darwinism. Our framework provides a new perspective to interpret known and future results in the context of quantum objectivity, paving the way for a deeper understanding of the emergence of classicality from the quantum realm.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Spengler2023,

title = {Optical solitons in curved spacetime},

author = {Felix Spengler and Alessio Belenchia and Dennis Rätzel and Daniel Braun},

doi = {10.1088/1361-6382/acdd43},

issn = {1361-6382},

year  = {2023},

date = {2023-07-20},

journal = {Class. Quantum Grav.},

volume = {40},

number = {14},

publisher = {IOP Publishing},

abstract = {Abstract

               Light propagation in curved spacetime is at the basis of some of the most stringent tests of Einstein’s general relativity. At the same time, light propagation in media is at the basis of several communication systems. Given the ubiquity of the gravitational field, and the exquisite level of sensitivity of optical measurements, the time is ripe for investigations combining these two aspects and studying light propagation in media located in curved spacetime. In this work, we focus on the effect of a weak gravitational field on the propagation of optical solitons in non-linear optical media. We derive a non-linear Schrödinger equation describing the propagation of an optical pulse in an effective, gradient-index medium in flat spacetime, encoding both the material properties and curved spacetime effects. In analyzing the special case of propagation in a 1D optical fiber, we also include the effect of mechanical deformations and show it to be the dominant effect for a fiber oriented in the radial direction in Schwarzschild spacetime.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{LoMonaco2023,

title = {Quantum scrambling via accessible tripartite information},

author = {Gabriele Lo Monaco and Luca Innocenti and Dario Cilluffo and Dario A Chisholm and Salvatore Lorenzo and G Massimo Palma},

doi = {10.1088/2058-9565/accd92},

issn = {2058-9565},

year  = {2023},

date = {2023-07-01},

journal = {Quantum Sci. Technol.},

volume = {8},

number = {3},

publisher = {IOP Publishing},

abstract = {Abstract

               Quantum information scrambling (QIS), from the perspective of quantum information theory, is generally understood as local non-retrievability of information evolved through some dynamical process, and is often quantified via entropic quantities such as the tripartite information. We argue that this approach comes with a number of issues, in large part due to its reliance on quantum mutual informations, which do not faithfully quantify correlations directly retrievable via measurements, and in part due to the specific methodology used to compute tripartite informations of the studied dynamics. We show that these issues can be overcome by using accessible mutual informations, defining corresponding ‘accessible tripartite informations’, and provide explicit examples of dynamics whose scrambling properties are not properly quantified by the standard tripartite information. Our results lay the groundwork for a more profound understanding of what QIS represents, and reveal a number of promising, as of yet unexplored, venues for further research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DiBartolomeo2023,

title = {Linear-friction many-body equation for dissipative spontaneous wave-function collapse},

author = {Giovanni Di Bartolomeo and Matteo Carlesso and Kristian Piscicchia and Catalina Curceanu and Maaneli Derakhshani and Lajos Diósi},

doi = {10.1103/physreva.108.012202},

issn = {2469-9934},

year  = {2023},

date = {2023-07-00},

journal = {Phys. Rev. A},

volume = {108},

number = {1},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gundhi2023,

title = {Motion of an electron through vacuum fluctuations},

author = {Anirudh Gundhi and Angelo Bassi},

doi = {10.1103/physreva.107.062801},

issn = {2469-9934},

year  = {2023},

date = {2023-06-00},

journal = {Phys. Rev. A},

volume = {107},

number = {6},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Donadi2023,

title = {Collapse Dynamics Are Diffusive},

author = {Sandro Donadi and Luca Ferialdi and Angelo Bassi},

doi = {10.1103/physrevlett.130.230202},

issn = {1079-7114},

year  = {2023},

date = {2023-06-00},

journal = {Phys. Rev. Lett.},

volume = {130},

number = {23},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2023,

title = {Quantifying protocol efficiency: A thermodynamic figure of merit for classical and quantum state-transfer protocols},

author = {Qiongyuan Wu and Mario A. Ciampini and Mauro Paternostro and Matteo Carlesso},

doi = {10.1103/physrevresearch.5.023117},

issn = {2643-1564},

year  = {2023},

date = {2023-05-00},

journal = {Phys. Rev. Research},

volume = {5},

number = {2},

publisher = {American Physical Society (APS)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Brown2023,

title = {Optimal quantum control via genetic algorithms for quantum state engineering in driven-resonator mediated networks},

author = {Jonathon Brown and Mauro Paternostro and Alessandro Ferraro},

doi = {10.1088/2058-9565/acb2f2},

issn = {2058-9565},

year  = {2023},

date = {2023-04-01},

journal = {Quantum Sci. Technol.},

volume = {8},

number = {2},

publisher = {IOP Publishing},

abstract = {Abstract

               We employ a machine learning-enabled approach to quantum state engineering based on evolutionary algorithms. In particular, we focus on superconducting platforms and consider a network of qubits—encoded in the states of artificial atoms with no direct coupling—interacting via a common single-mode driven microwave resonator. The qubit-resonator couplings are assumed to be in the resonant regime and tunable in time. A genetic algorithm is used in order to find the functional time-dependence of the couplings that optimise the fidelity between the evolved state and a variety of targets, including three-qubit GHZ and Dicke states and four-qubit graph states. We observe high quantum fidelities (above 0.96 in the worst case setting of a system of effective dimension 96), fast preparation times, and resilience to noise, despite the algorithm being trained in the ideal noise-free setting. These results show that the genetic algorithms represent an effective approach to control quantum systems of large dimensions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bassi2023,

title = {Collapse Models: A Theoretical, Experimental and Philosophical Review},

author = {Angelo Bassi and Mauro Dorato and Hendrik Ulbricht},

doi = {10.3390/e25040645},

issn = {1099-4300},

year  = {2023},

date = {2023-04-00},

journal = {Entropy},

volume = {25},

number = {4},

publisher = {MDPI AG},

abstract = {In this paper, we review and connect the three essential conditions needed by the collapse model to achieve a complete and exact formulation, namely the theoretical, the experimental, and the ontological ones. These features correspond to the three parts of the paper. In any empirical science, the first two features are obviously connected but, as is well known, among the different formulations and interpretations of non-relativistic quantum mechanics, only collapse models, as the paper well illustrates with a richness of details, have experimental consequences. Finally, we show that a clarification of the ontological intimations of collapse models is needed for at least three reasons: (1) to respond to the indispensable task of answering the question ’what are collapse models (and in general any physical theory) about?’; (2) to achieve a deeper understanding of their different formulations; (3) to enlarge the panorama of possible readings of a theory, which historically has often played a fundamental heuristic role.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Marchese2023,

title = {Optomechanics-Based Quantum Estimation Theory for Collapse Models},

author = {Marta Maria Marchese and Alessio Belenchia and Mauro Paternostro},

doi = {10.3390/e25030500},

issn = {1099-4300},

year  = {2023},

date = {2023-03-00},

journal = {Entropy},

volume = {25},

number = {3},

publisher = {MDPI AG},

abstract = {We make use of the powerful formalism of quantum parameter estimation to assess the characteristic rates of a continuous spontaneous localization (CSL) model affecting the motion of a massive mechanical system. We show that a study performed in non-equilibrium conditions unveils the advantages provided by the use of genuinely quantum resources—such as quantum correlations—in estimating the CSL-induced diffusion rate. In stationary conditions, instead, the gap between quantum performance and a classical scheme disappears. Our investigation contributes to the ongoing effort aimed at identifying suitable conditions for the experimental assessment of collapse models.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ribezzo2022,

title = {Deploying an Inter‐European Quantum Network},

author = {Domenico Ribezzo and Mujtaba Zahidy and Ilaria Vagniluca and Nicola Biagi and Saverio Francesconi and Tommaso Occhipinti and Leif K. Oxenløwe and Martin Lončarić and Ivan Cvitić and Mario Stipčević and Žiga Pušavec and Rainer Kaltenbaek and Anton Ramšak and Francesco Cesa and Giorgio Giorgetti and Francesco Scazza and Angelo Bassi and Paolo De Natale and Francesco Saverio Cataliotti and Massimo Inguscio and Davide Bacco and Alessandro Zavatta},

doi = {10.1002/qute.202200061},

issn = {2511-9044},

year  = {2023},

date = {2023-02-00},

journal = {Adv Quantum Tech},

volume = {6},

number = {2},

publisher = {Wiley},

abstract = {AbstractAround 40 years have passed since the first pioneering works introduced the possibility of using quantum physics to enhance communications safety. Nowadays, quantum key distribution (QKD) exited the physics laboratories to become a mature technology, triggering the attention of States, military forces, banks, and private corporations. This work takes on the challenge of bringing QKD closer to a consumer technology: deployed optical fibers by telecommunication companies of different States have been used to realize a quantum network, the first‐ever connecting three different countries. This work also emphasizes the necessity of networks where QKD can come up besides classical communications, whose coexistence currently represents the main limitation of this technology. This network connects Trieste to Rijeka and Ljubljana via a trusted node in Postojna. A key rate of over 3 kbps in the shortest link and a 7‐hour‐long measurement demonstrate the system's stability and reliability. The network has been used to present the QKD at the G20 Digital Ministers' Meeting in Trieste. The experimental results, together with the interest that one of the most important events of international politics has attracted, showcase the maturity of the QKD technology bundle, placing it in the spotlight for consumer applications in the near term.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}