Pub Date : 2025-10-14DOI: 10.1038/s41534-025-01103-z
Mateusz Kuniej, Paweł Machnikowski, Michał Gawełczyk
State transfer between different quantum systems is key for successful quantum technologies. Over long distances, photons are irreplaceable, but on short ranges in miniaturized complex devices or hybrid systems, coupling via orders of magnitude shorter-wavelength acoustic waves has great potential. With interfaces to light, acoustic waves, and more, optically active quantum dots (QDs) are essential for multi-component systems. Here, we propose a hybrid acousto-optical method for non-resonant QD charge state control, extending the recent all-optical swing-up state preparation. We show that exciton and biexciton states, or other superpositions of charge states, can be prepared. Each field can act as a trigger, allowing for the implementation of either an optically gated acoustic control or the opposite scheme, where an optical pulse controls the transition during acoustic modulation. Thus, we introduce acoustic state control into a system that lacks direct acoustic coupling between the states. The method does not rely on pulse shaping and is expected to work with arbitrary pulse shapes as long as the optical dressing is performed quasi-adiabatically. Evaluating the phonon impact, we find an almost decoherence-free exciton preparation even at elevated temperatures with current QD and acoustic technology. This approach may also pave the way for optically controlled entanglement between emitters and acoustic modes, and further on-chip state transfer via quantum acoustic buses.
{"title":"Hybrid acousto-optical swing-up state control in a quantum dot","authors":"Mateusz Kuniej, Paweł Machnikowski, Michał Gawełczyk","doi":"10.1038/s41534-025-01103-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01103-z","url":null,"abstract":"State transfer between different quantum systems is key for successful quantum technologies. Over long distances, photons are irreplaceable, but on short ranges in miniaturized complex devices or hybrid systems, coupling via orders of magnitude shorter-wavelength acoustic waves has great potential. With interfaces to light, acoustic waves, and more, optically active quantum dots (QDs) are essential for multi-component systems. Here, we propose a hybrid acousto-optical method for non-resonant QD charge state control, extending the recent all-optical swing-up state preparation. We show that exciton and biexciton states, or other superpositions of charge states, can be prepared. Each field can act as a trigger, allowing for the implementation of either an optically gated acoustic control or the opposite scheme, where an optical pulse controls the transition during acoustic modulation. Thus, we introduce acoustic state control into a system that lacks direct acoustic coupling between the states. The method does not rely on pulse shaping and is expected to work with arbitrary pulse shapes as long as the optical dressing is performed quasi-adiabatically. Evaluating the phonon impact, we find an almost decoherence-free exciton preparation even at elevated temperatures with current QD and acoustic technology. This approach may also pave the way for optically controlled entanglement between emitters and acoustic modes, and further on-chip state transfer via quantum acoustic buses.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"136 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145382407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1038/s41534-025-01077-y
F. Bemani, A. A. Rakhubovsky, R. Filip
Optomechanics with levitated nanoparticles is a promising way to combine very different types of quantum non-Gaussian aspects induced by continuous dynamics in a nonlinear or time-varying potential with the ones coming from discrete quantum elements in dynamics or measurement. First, it is necessary to prepare quantum non-Gaussian states using both methods. The nonlinear and time-varying potentials have been widely analyzed for this purpose. However, feasible preparation of provably quantum non-Gaussian states in a single mechanical mode using discrete photon detection has not been proposed yet for optical levitation. We explore pulsed optomechanical interactions combined with non-linear photon detection techniques to approach mechanical Fock states and confirm their quantum non-Gaussianity. We also predict the conditions under which the optomechanical interaction can induce multiple-phonon addition processes, which are relevant for n-phonon quantum non-Gaussianity. The practical applicability of quantum non-Gaussian states for sensing phase-randomized displacements is shown. Besides such applications, generating quantum non-Gaussian states of levitated nanoparticles can help to study fundamental questions of quantum thermodynamics, and macroscopic quantum effects.
{"title":"Heralded quantum non-Gaussian states in pulsed levitating optomechanics","authors":"F. Bemani, A. A. Rakhubovsky, R. Filip","doi":"10.1038/s41534-025-01077-y","DOIUrl":"https://doi.org/10.1038/s41534-025-01077-y","url":null,"abstract":"Optomechanics with levitated nanoparticles is a promising way to combine very different types of quantum non-Gaussian aspects induced by continuous dynamics in a nonlinear or time-varying potential with the ones coming from discrete quantum elements in dynamics or measurement. First, it is necessary to prepare quantum non-Gaussian states using both methods. The nonlinear and time-varying potentials have been widely analyzed for this purpose. However, feasible preparation of provably quantum non-Gaussian states in a single mechanical mode using discrete photon detection has not been proposed yet for optical levitation. We explore pulsed optomechanical interactions combined with non-linear photon detection techniques to approach mechanical Fock states and confirm their quantum non-Gaussianity. We also predict the conditions under which the optomechanical interaction can induce multiple-phonon addition processes, which are relevant for <jats:italic>n</jats:italic>-phonon quantum non-Gaussianity. The practical applicability of quantum non-Gaussian states for sensing phase-randomized displacements is shown. Besides such applications, generating quantum non-Gaussian states of levitated nanoparticles can help to study fundamental questions of quantum thermodynamics, and macroscopic quantum effects.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"58 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145382408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1038/s41534-025-01006-z
Darren W. Moore, Radim Filip
Low-order nonlinear phase gates allow the construction of versatile higher-order nonlinearities for bosonic systems and grant access to continuous variable quantum simulations of many unexplored aspects of nonlinear quantum dynamics. The resulting nonlinear transformations produce, even with small strength, multiple regions of negativity in the Wigner function and thus show an immediate departure from classical phase space. Towards the development of realistic, bounded versions of these gates we show that the action of a quartic-bounded cubic gate on an arbitrary multimode quantum state in phase space can be understood as an Airy transform of the Wigner function. This toolbox generalises the symplectic transformations associated with Gaussian operations and allows for the practical calculation, analysis and interpretation of explicit Wigner functions and the quantum non-Gaussian phenomena resulting from bounded nonlinear potentials.
{"title":"Nonlinear phase gates as Airy transforms of the Wigner function","authors":"Darren W. Moore, Radim Filip","doi":"10.1038/s41534-025-01006-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01006-z","url":null,"abstract":"Low-order nonlinear phase gates allow the construction of versatile higher-order nonlinearities for bosonic systems and grant access to continuous variable quantum simulations of many unexplored aspects of nonlinear quantum dynamics. The resulting nonlinear transformations produce, even with small strength, multiple regions of negativity in the Wigner function and thus show an immediate departure from classical phase space. Towards the development of realistic, bounded versions of these gates we show that the action of a quartic-bounded cubic gate on an arbitrary multimode quantum state in phase space can be understood as an Airy transform of the Wigner function. This toolbox generalises the symplectic transformations associated with Gaussian operations and allows for the practical calculation, analysis and interpretation of explicit Wigner functions and the quantum non-Gaussian phenomena resulting from bounded nonlinear potentials.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"2 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145381791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-03DOI: 10.1038/s41534-025-01117-7
Cong-Gang Song, Qing-yu Cai
{"title":"Author Correction: Excessive precision compromises accuracy even with unlimited resources due to the trade-off in quantum metrology","authors":"Cong-Gang Song, Qing-yu Cai","doi":"10.1038/s41534-025-01117-7","DOIUrl":"https://doi.org/10.1038/s41534-025-01117-7","url":null,"abstract":"","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"61 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145381795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-02DOI: 10.1038/s41534-025-01102-0
Felix-Ekkehard von Horstig, Lorenzo Peri, Virginia N. Ciriano-Tejel, Sylvain Barraud, Jason A. W. Robinson, Monica Benito, Frederico Martins, M. Fernando Gonzalez-Zalba
In semiconductor nanostructures, spin blockade (SB) is the most scalable mechanism for electrical spin readout, requiring only two bound spins for its implementation. In conjunction with charge sensing techniques, SB has led to high-fidelity readout of spins in semiconductor-based quantum processors. However, various mechanisms may lift SB, such as strong spin-orbit coupling (SOC) or low-lying excited states, hence posing challenges to perform spin readout at scale and with high fidelity in such systems. Here, we present a method, based on the dependence of the two-spin system polarizability on energy detuning, to perform spin state readout even when SB lifting mechanisms are dominant. It leverages SB lifting as a resource to detect selectively different spin measurement outcomes. We demonstrate the method using a hybrid system formed by a quantum dot (QD) and a Boron acceptor in a silicon p-type transistor and show spin-selective readout of different spin states under SB lifting conditions due to (i) SOC and (ii) low-lying orbital states in the QD. We further use the method to determine the detuning-dependent spin relaxation time of 0.1–8 μs. Our method should help perform projective spin measurements with high spin-to-charge conversion fidelity in systems subject to strong SOC, will facilitate state leakage detection and enable complete readout of two-spin states.
{"title":"Electrical readout of spins in the absence of spin blockade","authors":"Felix-Ekkehard von Horstig, Lorenzo Peri, Virginia N. Ciriano-Tejel, Sylvain Barraud, Jason A. W. Robinson, Monica Benito, Frederico Martins, M. Fernando Gonzalez-Zalba","doi":"10.1038/s41534-025-01102-0","DOIUrl":"https://doi.org/10.1038/s41534-025-01102-0","url":null,"abstract":"In semiconductor nanostructures, spin blockade (SB) is the most scalable mechanism for electrical spin readout, requiring only two bound spins for its implementation. In conjunction with charge sensing techniques, SB has led to high-fidelity readout of spins in semiconductor-based quantum processors. However, various mechanisms may lift SB, such as strong spin-orbit coupling (SOC) or low-lying excited states, hence posing challenges to perform spin readout at scale and with high fidelity in such systems. Here, we present a method, based on the dependence of the two-spin system polarizability on energy detuning, to perform spin state readout even when SB lifting mechanisms are dominant. It leverages SB lifting as a resource to detect selectively different spin measurement outcomes. We demonstrate the method using a hybrid system formed by a quantum dot (QD) and a Boron acceptor in a silicon p-type transistor and show spin-selective readout of different spin states under SB lifting conditions due to (i) SOC and (ii) low-lying orbital states in the QD. We further use the method to determine the detuning-dependent spin relaxation time of 0.1–8 <jats:italic>μ</jats:italic>s. Our method should help perform projective spin measurements with high spin-to-charge conversion fidelity in systems subject to strong SOC, will facilitate state leakage detection and enable complete readout of two-spin states.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"1 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145381796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-26DOI: 10.1038/s41534-025-01100-2
Oliver M Crampton,Toby J Dowling,Thomas Roger,Peter R Smith,James F Dynes,Matthew S Winnel,Davide G Marangon,Mirko Sanzaro,Ravinder Singh,Chithrabhanu Perumangatt,Joseph A Dolphin,Taofiq K Paraiso,Andrew J Shields
We introduce a low size, weight and power quantum random number generator (QRNG) utilizing compact integrated photonic asymmetric Mach-Zehnder interferometers (AMZIs). Our QRNG is based on phase-diffusion in two gain-switched lasers interfered within two separate chip-AMZIs. By substituting the high-bit analog-to-digital converters, typically employed to digitize the random intensity signal from each laser, with clocked comparators we significantly reduce both the complexity and power consumption of the device. Furthermore, by performing the exclusive OR (XOR) operation on the output random bits of each channel we are able to reduce the processing requirements. The QRNG architecture can be integrated with an overhead power consumption of just 7.93 W, accounting for the opto-electronics and FPGA implementation, providing fast random number generation at up to 2 Gbps. We demonstrate the real-time seeding of a free-space decoy-state quantum key distribution system using our QRNG. Our design and implementation provides a practical solution for QRNGs requiring low-power and high bit rates. This advancement is important for practical QRNGs and particularly for application in resource-constrained environments such as space-based quantum key distribution.
{"title":"A 2-Gbps low-SWaP quantum random number generator with photonic integrated circuits for satellite applications.","authors":"Oliver M Crampton,Toby J Dowling,Thomas Roger,Peter R Smith,James F Dynes,Matthew S Winnel,Davide G Marangon,Mirko Sanzaro,Ravinder Singh,Chithrabhanu Perumangatt,Joseph A Dolphin,Taofiq K Paraiso,Andrew J Shields","doi":"10.1038/s41534-025-01100-2","DOIUrl":"https://doi.org/10.1038/s41534-025-01100-2","url":null,"abstract":"We introduce a low size, weight and power quantum random number generator (QRNG) utilizing compact integrated photonic asymmetric Mach-Zehnder interferometers (AMZIs). Our QRNG is based on phase-diffusion in two gain-switched lasers interfered within two separate chip-AMZIs. By substituting the high-bit analog-to-digital converters, typically employed to digitize the random intensity signal from each laser, with clocked comparators we significantly reduce both the complexity and power consumption of the device. Furthermore, by performing the exclusive OR (XOR) operation on the output random bits of each channel we are able to reduce the processing requirements. The QRNG architecture can be integrated with an overhead power consumption of just 7.93 W, accounting for the opto-electronics and FPGA implementation, providing fast random number generation at up to 2 Gbps. We demonstrate the real-time seeding of a free-space decoy-state quantum key distribution system using our QRNG. Our design and implementation provides a practical solution for QRNGs requiring low-power and high bit rates. This advancement is important for practical QRNGs and particularly for application in resource-constrained environments such as space-based quantum key distribution.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"78 1","pages":"153"},"PeriodicalIF":7.6,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-02DOI: 10.1038/s41534-025-01101-1
Zhen Qin, Joseph M. Lukens, Brian T. Kirby, Zhihui Zhu
While classical shadows can efficiently predict key quantum state properties, their suitability for certified quantum state tomography remains uncertain. In this paper, we address this challenge by introducing a projected classical shadow (PCS) that extends the standard classical shadow by incorporating a projection step onto the target subspace. For a general quantum state consisting of n qubits, our method requires a minimum of O(4n) total state copies to achieve a bounded recovery error in the Frobenius norm between the reconstructed and true density matrices, reducing to O(2nr) for states of rank r < 2n—meeting information-theoretic optimal bounds in both cases. For matrix product operator states, we demonstrate that the PCS can recover the ground-truth state with O(n2) total state copies, improving upon the previously established Haar-random bound of O(n3). Numerical simulations validate our scaling results and demonstrate the practical accuracy of the proposed PCS method.
{"title":"Enhancing quantum state reconstruction with structured classical shadows","authors":"Zhen Qin, Joseph M. Lukens, Brian T. Kirby, Zhihui Zhu","doi":"10.1038/s41534-025-01101-1","DOIUrl":"https://doi.org/10.1038/s41534-025-01101-1","url":null,"abstract":"<p>While classical shadows can efficiently predict key quantum state properties, their suitability for certified quantum state tomography remains uncertain. In this paper, we address this challenge by introducing a projected classical shadow (PCS) that extends the standard classical shadow by incorporating a projection step onto the target subspace. For a general quantum state consisting of <i>n</i> qubits, our method requires a minimum of <i>O</i>(4<sup><i>n</i></sup>) total state copies to achieve a bounded recovery error in the Frobenius norm between the reconstructed and true density matrices, reducing to <i>O</i>(2<sup><i>n</i></sup><i>r</i>) for states of rank <i>r</i> < 2<sup><i>n</i></sup>—meeting information-theoretic optimal bounds in both cases. For matrix product operator states, we demonstrate that the PCS can recover the ground-truth state with <i>O</i>(<i>n</i><sup>2</sup>) total state copies, improving upon the previously established Haar-random bound of <i>O</i>(<i>n</i><sup>3</sup>). Numerical simulations validate our scaling results and demonstrate the practical accuracy of the proposed PCS method.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"11 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144928296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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