Pub Date : 2025-12-05DOI: 10.1088/2058-9565/ae24a7
Fabrizio Sgobba, Francesco Di Lena, Danilo Triggiani, Deborah Katia Pallotti, Cosmo Lupo, Piergiorgio Daniele, Gennaro Fratta, Giulia Acconcia, Ivan Rech and Luigi Santamaria Amato
We demonstrate an experimental scheme for high-precision position measurements based on transverse-momentum-resolved two-photon interferometry with independent photons and single photon avalanche diode (SPAD) arrays. Our scheme extends the operative range of Hong–Ou–Mandel interferometry beyond its intrinsic constraints due to photons indistinguishability, paving the way to applications in high-resolution imaging. We assess the experimental results against the ultimate precision bounds as determined by quantum estimation theory. Our experiment ultimately proves that transverse-momentum resolved measurements of fourth-order correlations in the fields can be employed to overcome spatial distinguishability between independent photons. The relevance of our results extends beyond sensing and imaging towards quantum information processing, as we show that partial photon distinguishability and entanglement impurity are not necessarily a nuisance in a technique that relies on two-photon interference.
{"title":"Momentum-resolved two photon interference of weak coherent states","authors":"Fabrizio Sgobba, Francesco Di Lena, Danilo Triggiani, Deborah Katia Pallotti, Cosmo Lupo, Piergiorgio Daniele, Gennaro Fratta, Giulia Acconcia, Ivan Rech and Luigi Santamaria Amato","doi":"10.1088/2058-9565/ae24a7","DOIUrl":"https://doi.org/10.1088/2058-9565/ae24a7","url":null,"abstract":"We demonstrate an experimental scheme for high-precision position measurements based on transverse-momentum-resolved two-photon interferometry with independent photons and single photon avalanche diode (SPAD) arrays. Our scheme extends the operative range of Hong–Ou–Mandel interferometry beyond its intrinsic constraints due to photons indistinguishability, paving the way to applications in high-resolution imaging. We assess the experimental results against the ultimate precision bounds as determined by quantum estimation theory. Our experiment ultimately proves that transverse-momentum resolved measurements of fourth-order correlations in the fields can be employed to overcome spatial distinguishability between independent photons. The relevance of our results extends beyond sensing and imaging towards quantum information processing, as we show that partial photon distinguishability and entanglement impurity are not necessarily a nuisance in a technique that relies on two-photon interference.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145673644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-12-04DOI: 10.1088/2058-9565/ae24a8
Naman Jain and Amir Kalev
We introduce quantum feature extraction (QuFeX), a novel quantum machine learning module. The proposed module enables feature extraction in a reduced-dimensional space, significantly decreasing the number of parallel evaluations required in typical quantum convolutional neural network (NNs) architectures. Its design allows seamless integration into deep classical NNs, making it particularly suitable for hybrid quantum–classical models. As an application of QuFeX, we propose Qu-Net—a hybrid architecture which integrates QuFeX at the bottleneck of a U-Net architecture. The latter is widely used for image segmentation tasks such as medical imaging and autonomous driving. Our numerical analysis indicates that the Qu-Net can achieve superior segmentation performance compared to a U-Net baseline. These results highlight the potential of QuFeX to enhance deep NNs by leveraging hybrid computational paradigms, providing a path towards a robust framework for real-world applications requiring precise feature extraction.
{"title":"QuFeX: quantum feature extraction module for hybrid quantum-classical deep neural networks","authors":"Naman Jain and Amir Kalev","doi":"10.1088/2058-9565/ae24a8","DOIUrl":"https://doi.org/10.1088/2058-9565/ae24a8","url":null,"abstract":"We introduce quantum feature extraction (QuFeX), a novel quantum machine learning module. The proposed module enables feature extraction in a reduced-dimensional space, significantly decreasing the number of parallel evaluations required in typical quantum convolutional neural network (NNs) architectures. Its design allows seamless integration into deep classical NNs, making it particularly suitable for hybrid quantum–classical models. As an application of QuFeX, we propose Qu-Net—a hybrid architecture which integrates QuFeX at the bottleneck of a U-Net architecture. The latter is widely used for image segmentation tasks such as medical imaging and autonomous driving. Our numerical analysis indicates that the Qu-Net can achieve superior segmentation performance compared to a U-Net baseline. These results highlight the potential of QuFeX to enhance deep NNs by leveraging hybrid computational paradigms, providing a path towards a robust framework for real-world applications requiring precise feature extraction.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"34 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145664767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-12-03DOI: 10.1088/2058-9565/ae2291
Carlos Barahona-Pascual, Hong Jiang, Alan C Santos and Juan José García-Ripoll
This work introduces a theoretical framework to model the collective dynamics of quantum emitters in highly non-Markovian environments, interacting through the exchange of photons with significant retardations. The formalism consists on a set of coupled delay differential equations for the emitter’s raising/lowering operators , supplemented by input–output relations that describe the field mediating the interactions. These equations capture the dynamics of both linear (bosonic) and nonlinear (two-level) emitter arrays. It is exact in some limits—e.g. bosonic emitters or generic systems with up to one collective excitation—and can be integrated to provide accurate results for larger numbers of photons. These equations support a study of collective spontaneous emission of emitter arrays in open waveguide-QED environments. This study uncovers an effect we term cascaded super- and sub-radiance, characterized by light-cone-limited propagation and increasingly correlated photon emission across distant emitters. The collective nature of this dynamics for two-level systems is evident both in the enhancement of collective emission rates, as well as in a superradiant burst with a faster than linear growth. While these effects should be observable in existing circuit QED devices or slight generalizations thereof, the formalism put forward in this work can be extended to model other systems such as network of quantum emitters or the generation of correlated photon states.
{"title":"Time-delayed collective dynamics in waveguide QED and bosonic quantum networks","authors":"Carlos Barahona-Pascual, Hong Jiang, Alan C Santos and Juan José García-Ripoll","doi":"10.1088/2058-9565/ae2291","DOIUrl":"https://doi.org/10.1088/2058-9565/ae2291","url":null,"abstract":"This work introduces a theoretical framework to model the collective dynamics of quantum emitters in highly non-Markovian environments, interacting through the exchange of photons with significant retardations. The formalism consists on a set of coupled delay differential equations for the emitter’s raising/lowering operators , supplemented by input–output relations that describe the field mediating the interactions. These equations capture the dynamics of both linear (bosonic) and nonlinear (two-level) emitter arrays. It is exact in some limits—e.g. bosonic emitters or generic systems with up to one collective excitation—and can be integrated to provide accurate results for larger numbers of photons. These equations support a study of collective spontaneous emission of emitter arrays in open waveguide-QED environments. This study uncovers an effect we term cascaded super- and sub-radiance, characterized by light-cone-limited propagation and increasingly correlated photon emission across distant emitters. The collective nature of this dynamics for two-level systems is evident both in the enhancement of collective emission rates, as well as in a superradiant burst with a faster than linear growth. While these effects should be observable in existing circuit QED devices or slight generalizations thereof, the formalism put forward in this work can be extended to model other systems such as network of quantum emitters or the generation of correlated photon states.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"20 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-12-01DOI: 10.1088/2058-9565/ae21ff
Valentin Guichard, Leonid Vidro, Dario A Fioretto, Petr Steindl, Daniel Istrati, Yehuda Pilnyak, Mathias Pont, Martina Morassi, Aristide Lemaître, Isabelle Sagnes, Niccolo Somaschi, Nadia Belabas, Hagai S Eisenberg and Pascale Senellart
Quantum states of light with many entangled photons are key resources for photonic quantum computing and quantum communication. In this work, we exploit a highly resource-efficient generation scheme based on a linear optical circuit embedding a fibered delay loop acting as a quantum memory. The single photons are generated with a bright single-photon source based on a semiconductor quantum dot, allowing to perform the entangling scheme up to 6 photons. We demonstrate 2, 3, 4 and 6-photon entanglement generation at respective rates of 6 kHz, 120 Hz, 2.2 Hz, and 2 mHz, corresponding to an average scaling ratio of 46. We introduce a method for real-time control of entanglement generation based on partially post-selected measurements. The visibility of such measurements enables discrimination and correcting for experimental phase drifts or entangling gate fidelity variations, and thus carries faithful information to monitor the entanglement process, an important feature for the practical implementation of photonic measurement-based quantum computation.
{"title":"Monitoring the generation of photonic linear cluster states with partial measurements","authors":"Valentin Guichard, Leonid Vidro, Dario A Fioretto, Petr Steindl, Daniel Istrati, Yehuda Pilnyak, Mathias Pont, Martina Morassi, Aristide Lemaître, Isabelle Sagnes, Niccolo Somaschi, Nadia Belabas, Hagai S Eisenberg and Pascale Senellart","doi":"10.1088/2058-9565/ae21ff","DOIUrl":"https://doi.org/10.1088/2058-9565/ae21ff","url":null,"abstract":"Quantum states of light with many entangled photons are key resources for photonic quantum computing and quantum communication. In this work, we exploit a highly resource-efficient generation scheme based on a linear optical circuit embedding a fibered delay loop acting as a quantum memory. The single photons are generated with a bright single-photon source based on a semiconductor quantum dot, allowing to perform the entangling scheme up to 6 photons. We demonstrate 2, 3, 4 and 6-photon entanglement generation at respective rates of 6 kHz, 120 Hz, 2.2 Hz, and 2 mHz, corresponding to an average scaling ratio of 46. We introduce a method for real-time control of entanglement generation based on partially post-selected measurements. The visibility of such measurements enables discrimination and correcting for experimental phase drifts or entangling gate fidelity variations, and thus carries faithful information to monitor the entanglement process, an important feature for the practical implementation of photonic measurement-based quantum computation.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"218 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-12-01DOI: 10.1088/2058-9565/ae2200
K H Kua, Alessio Serafini and Marco G Genoni
According to the Maxwell demon paradigm, additional work can be extracted from a classical or quantum system by exploiting information obtained through measurements on a correlated ancillary system. In the quantum setting, the maximum work extractable via unitary operations in such measurement-assisted protocols is referred to as daemonic ergotropy. In this work, we explore this concept in the context of continuous-variable quantum systems, focusing on Gaussian states and general-dyne (Gaussian) measurements. We derive a general expression for the daemonic ergotropy and examine two key scenarios: (i) bipartite Gaussian states where a general-dyne measurement is performed on one of the two parties, and (ii) open Gaussian quantum systems under continuous general-dyne monitoring of the environment. Remarkably, we show that for single-mode Gaussian states, the ergotropy depends solely on the state’s energy and purity. This enables us to express the daemonic ergotropy as a simple function of the unconditional energy and the purity of the conditional states, revealing that enhanced daemonic work extraction is directly linked to measurement-induced purification. We illustrate our findings through two paradigmatic examples: extracting daemonic work from a two-mode squeezed thermal state and from a continuously monitored optical parametric oscillator. In both case we identify the optimal general-dyne strategies that maximize the conditional purity and, in turn, the daemonic ergotropy.
{"title":"Daemonic ergotropy of Gaussian quantum states and the role of measurement-induced purification via general-dyne detection","authors":"K H Kua, Alessio Serafini and Marco G Genoni","doi":"10.1088/2058-9565/ae2200","DOIUrl":"https://doi.org/10.1088/2058-9565/ae2200","url":null,"abstract":"According to the Maxwell demon paradigm, additional work can be extracted from a classical or quantum system by exploiting information obtained through measurements on a correlated ancillary system. In the quantum setting, the maximum work extractable via unitary operations in such measurement-assisted protocols is referred to as daemonic ergotropy. In this work, we explore this concept in the context of continuous-variable quantum systems, focusing on Gaussian states and general-dyne (Gaussian) measurements. We derive a general expression for the daemonic ergotropy and examine two key scenarios: (i) bipartite Gaussian states where a general-dyne measurement is performed on one of the two parties, and (ii) open Gaussian quantum systems under continuous general-dyne monitoring of the environment. Remarkably, we show that for single-mode Gaussian states, the ergotropy depends solely on the state’s energy and purity. This enables us to express the daemonic ergotropy as a simple function of the unconditional energy and the purity of the conditional states, revealing that enhanced daemonic work extraction is directly linked to measurement-induced purification. We illustrate our findings through two paradigmatic examples: extracting daemonic work from a two-mode squeezed thermal state and from a continuously monitored optical parametric oscillator. In both case we identify the optimal general-dyne strategies that maximize the conditional purity and, in turn, the daemonic ergotropy.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"111 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-11-28DOI: 10.1088/2058-9565/ae20b6
Wolfgang Dür
We propose a quantum computation architecture based on geometries with nearest-neighbor interactions, including e.g. planar structures. We show how to efficiently split the role of qubits into data and entanglement-generation qubits. Multipartite entangled states, e.g. 2D cluster states, are generated among the latter, and flexibly transformed via mid-circuit measurements to multiple, long-ranged Bell states, which are used to perform several two-qubit gates in parallel on data qubits. We introduce planar architectures with n data and n auxiliary qubits that allow one to perform long-ranged two-qubit gates simultaneously, with only one round of nearest neighbor gates and one round of mid-circuit measurements. We also show that our approach is applicable in existing superconducting quantum computation architectures, with only a constant overhead.
{"title":"Long-ranged gates in quantum computation architectures with limited connectivity","authors":"Wolfgang Dür","doi":"10.1088/2058-9565/ae20b6","DOIUrl":"https://doi.org/10.1088/2058-9565/ae20b6","url":null,"abstract":"We propose a quantum computation architecture based on geometries with nearest-neighbor interactions, including e.g. planar structures. We show how to efficiently split the role of qubits into data and entanglement-generation qubits. Multipartite entangled states, e.g. 2D cluster states, are generated among the latter, and flexibly transformed via mid-circuit measurements to multiple, long-ranged Bell states, which are used to perform several two-qubit gates in parallel on data qubits. We introduce planar architectures with n data and n auxiliary qubits that allow one to perform long-ranged two-qubit gates simultaneously, with only one round of nearest neighbor gates and one round of mid-circuit measurements. We also show that our approach is applicable in existing superconducting quantum computation architectures, with only a constant overhead.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"150 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145611139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-11-27DOI: 10.1088/2058-9565/ae20b5
Diego García-Martín, Paolo Braccia and M Cerezo
Parametrized and random unitary (or orthogonal) n-qubit circuits play a central role in quantum information. As such, one could naturally assume that circuits implementing symplectic transformations would attract similar attention. However, this is not the case, as —the group of d × d unitary symplectic matrices—has thus far been overlooked. In this work, we aim at starting to fill this gap. We begin by presenting a universal set of generators for the symplectic algebra , consisting of one- and two-qubit Pauli operators acting on neighboring sites in a one-dimensional lattice. Here, we uncover two critical differences between such set, and equivalent ones for unitary and orthogonal circuits. Namely, we find that the operators in cannot generate arbitrary local symplectic unitaries and that they are not translationally invariant. We then review the Schur–Weyl duality between the symplectic group and the Brauer algebra, and use tools from Weingarten calculus to prove that Pauli measurements at the output of Haar random symplectic circuits can converge to Gaussian processes. As a by-product, such analysis provides us with concentration bounds for Pauli measurements in circuits that form t-designs over . To finish, we present tensor-network tools to analyze shallow random symplectic circuits, and we use these to numerically show that computational-basis measurements anti-concentrate at logarithmic depth.
{"title":"Architectures and random properties of symplectic quantum circuits","authors":"Diego García-Martín, Paolo Braccia and M Cerezo","doi":"10.1088/2058-9565/ae20b5","DOIUrl":"https://doi.org/10.1088/2058-9565/ae20b5","url":null,"abstract":"Parametrized and random unitary (or orthogonal) n-qubit circuits play a central role in quantum information. As such, one could naturally assume that circuits implementing symplectic transformations would attract similar attention. However, this is not the case, as —the group of d × d unitary symplectic matrices—has thus far been overlooked. In this work, we aim at starting to fill this gap. We begin by presenting a universal set of generators for the symplectic algebra , consisting of one- and two-qubit Pauli operators acting on neighboring sites in a one-dimensional lattice. Here, we uncover two critical differences between such set, and equivalent ones for unitary and orthogonal circuits. Namely, we find that the operators in cannot generate arbitrary local symplectic unitaries and that they are not translationally invariant. We then review the Schur–Weyl duality between the symplectic group and the Brauer algebra, and use tools from Weingarten calculus to prove that Pauli measurements at the output of Haar random symplectic circuits can converge to Gaussian processes. As a by-product, such analysis provides us with concentration bounds for Pauli measurements in circuits that form t-designs over . To finish, we present tensor-network tools to analyze shallow random symplectic circuits, and we use these to numerically show that computational-basis measurements anti-concentrate at logarithmic depth.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"29 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-11-27DOI: 10.1088/2058-9565/ae20b7
M Tahir Naseem
Controlling heat flow at the quantum level is essential for the development of next-generation thermal devices. We investigate thermal rectification in a quantum harmonic oscillator coupled to two thermal baths via both single-photon (linear) and two-photon (nonlinear) exchange processes. At low temperatures, rectification emerges from a state-dependent thermal blockade: the cold bath drives the oscillator into low-occupancy states, suppressing two-photon emission and impeding energy flow. At higher temperatures, rectification is governed by the asymmetric scaling of higher-order moments associated with two-photon absorption and emission. We systematically explore various bath coupling configurations and identify the conditions under which nonlinear dissipation leads to directional heat flow. Furthermore, we propose an implementation scheme based on coupling an auxiliary two-level system to the oscillator, enabling effective two-photon dissipation. We also extend our analysis to three-photon processes and show that rectification increases systematically with photon interaction order. These results contribute to the understanding of quantum heat transport in the presence of nonlinear dissipation and may support future efforts in nanoscale thermal rectification design.
{"title":"Quantum thermal rectification via state-dependent two-photon dissipation","authors":"M Tahir Naseem","doi":"10.1088/2058-9565/ae20b7","DOIUrl":"https://doi.org/10.1088/2058-9565/ae20b7","url":null,"abstract":"Controlling heat flow at the quantum level is essential for the development of next-generation thermal devices. We investigate thermal rectification in a quantum harmonic oscillator coupled to two thermal baths via both single-photon (linear) and two-photon (nonlinear) exchange processes. At low temperatures, rectification emerges from a state-dependent thermal blockade: the cold bath drives the oscillator into low-occupancy states, suppressing two-photon emission and impeding energy flow. At higher temperatures, rectification is governed by the asymmetric scaling of higher-order moments associated with two-photon absorption and emission. We systematically explore various bath coupling configurations and identify the conditions under which nonlinear dissipation leads to directional heat flow. Furthermore, we propose an implementation scheme based on coupling an auxiliary two-level system to the oscillator, enabling effective two-photon dissipation. We also extend our analysis to three-photon processes and show that rectification increases systematically with photon interaction order. These results contribute to the understanding of quantum heat transport in the presence of nonlinear dissipation and may support future efforts in nanoscale thermal rectification design.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"29 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145609758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-11-26DOI: 10.1088/2058-9565/ae20b9
Akihiro Mizutani, Shun Kawakami and Go Kato
The decoy-state Bennett–Brassard 1984 (BB84) quantum key distribution (QKD) protocol is widely regarded as the de facto standard for practical implementations. On the receiver side, passive basis choice is attractive because it significantly reduces the need for random number generators and eliminates the need for optical modulators. Despite these advantages, a finite-key analytical security proof for the decoy-state BB84 protocol, where the basis is chosen passively with a biased probability, has been lacking. In this work, we present a simple analytical finite-key security proof for this setting, yielding a closed-form secret-key rate formula that can be directly evaluated using experimentally accessible parameters. Numerical simulations show that the key rates of passive- and active-measurement implementations are nearly identical, indicating that passive measurement does not compromise key-generation efficiency in practical QKD systems.
{"title":"Finite-key security analysis of the decoy-state BB84 QKD with passive measurement","authors":"Akihiro Mizutani, Shun Kawakami and Go Kato","doi":"10.1088/2058-9565/ae20b9","DOIUrl":"https://doi.org/10.1088/2058-9565/ae20b9","url":null,"abstract":"The decoy-state Bennett–Brassard 1984 (BB84) quantum key distribution (QKD) protocol is widely regarded as the de facto standard for practical implementations. On the receiver side, passive basis choice is attractive because it significantly reduces the need for random number generators and eliminates the need for optical modulators. Despite these advantages, a finite-key analytical security proof for the decoy-state BB84 protocol, where the basis is chosen passively with a biased probability, has been lacking. In this work, we present a simple analytical finite-key security proof for this setting, yielding a closed-form secret-key rate formula that can be directly evaluated using experimentally accessible parameters. Numerical simulations show that the key rates of passive- and active-measurement implementations are nearly identical, indicating that passive measurement does not compromise key-generation efficiency in practical QKD systems.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145599362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-11-24DOI: 10.1088/2058-9565/ae1c68
Naeimeh Mohseni, Thomas Morstyn, Corey O’Meara, David Bucher, Jonas Nüßlein and Giorgio Cortiana
The formation of energy communities is pivotal for advancing decentralized and sustainable energy management. Within this context, coalition structure generation (CSG) emerges as a promising framework. The complexity of CSG grows rapidly with the number of agents, making classical solvers impractical for even moderate sizes. This suggests CSG as an ideal candidate for benchmarking quantum algorithms against classical ones. Facing ongoing challenges in attaining computational quantum advantage for exact optimization, we pivot our focus to benchmarking quantum and classical solvers for approximate optimization. Approximate optimization is particularly critical for industrial use cases requiring real-time optimization, where finding high-quality solutions quickly is often more valuable than achieving exact solutions more slowly. Our findings indicate that quantum annealing (QA) on DWave can achieve solutions of comparable quality to our best classical solver, but with more favorable runtime scaling, showcasing an advantage. This advantage is observed when compared to solvers, such as Tabu search, simulated annealing, and the state-of-the-art solver Gurobi in finding approximate solutions for energy community formation involving over 100 agents. DWave also surpasses 1-round QAOA on IBM hardware. Our findings represent the largest benchmark of quantum approximate optimizations for a real-world dense model beyond the hardware’s native topology, where D-Wave demonstrates a scaling advantage.
{"title":"Evidence of quantum scaling advantage in approximate optimization for energy coalition formation with 100+ agents","authors":"Naeimeh Mohseni, Thomas Morstyn, Corey O’Meara, David Bucher, Jonas Nüßlein and Giorgio Cortiana","doi":"10.1088/2058-9565/ae1c68","DOIUrl":"https://doi.org/10.1088/2058-9565/ae1c68","url":null,"abstract":"The formation of energy communities is pivotal for advancing decentralized and sustainable energy management. Within this context, coalition structure generation (CSG) emerges as a promising framework. The complexity of CSG grows rapidly with the number of agents, making classical solvers impractical for even moderate sizes. This suggests CSG as an ideal candidate for benchmarking quantum algorithms against classical ones. Facing ongoing challenges in attaining computational quantum advantage for exact optimization, we pivot our focus to benchmarking quantum and classical solvers for approximate optimization. Approximate optimization is particularly critical for industrial use cases requiring real-time optimization, where finding high-quality solutions quickly is often more valuable than achieving exact solutions more slowly. Our findings indicate that quantum annealing (QA) on DWave can achieve solutions of comparable quality to our best classical solver, but with more favorable runtime scaling, showcasing an advantage. This advantage is observed when compared to solvers, such as Tabu search, simulated annealing, and the state-of-the-art solver Gurobi in finding approximate solutions for energy community formation involving over 100 agents. DWave also surpasses 1-round QAOA on IBM hardware. Our findings represent the largest benchmark of quantum approximate optimizations for a real-world dense model beyond the hardware’s native topology, where D-Wave demonstrates a scaling advantage.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"66 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145583604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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