Pub Date : 2026-01-28DOI: 10.1088/2058-9565/ae34e1
Yan Lu and Xiao-Feng Shi
Large-scale Greenberger–Horne–Zeilinger (GHZ) state is useful for quantum technologies but difficult to be prepared. Here, we propose fast measurement-based preparation of large-scale GHZ states by a four-qubit quantum phase gate with nuclear-spin qubits of alkaline-earth-like atoms, which is named as quantum ferromagnetic gate due to its analogy to the alignment of molecular magnetic moments in a classical magnet. A high-fidelity Rydberg-mediated QFG can be realized in a time of with the maximal Rydberg Rabi frequency. From a product state of three data atoms and one ancilla atom, a gluing circuit with one QFG, two single-qubit gates, and a projective measurement of the ancilla can generate a 3-qubit GHZ state, and repetition of this gluing circuit can lead to 9, 27, 81, 243 -qubit GHZ states. Analyses based on currently available techniques show that a 243-qubit GHZ state is realizable, and more qubits can be entangled with higher detection fidelity.
{"title":"Fast measurement-based generation of large-scale Greenberger–Horne–Zeilinger state with atomic nuclear-spin qubits","authors":"Yan Lu and Xiao-Feng Shi","doi":"10.1088/2058-9565/ae34e1","DOIUrl":"https://doi.org/10.1088/2058-9565/ae34e1","url":null,"abstract":"Large-scale Greenberger–Horne–Zeilinger (GHZ) state is useful for quantum technologies but difficult to be prepared. Here, we propose fast measurement-based preparation of large-scale GHZ states by a four-qubit quantum phase gate with nuclear-spin qubits of alkaline-earth-like atoms, which is named as quantum ferromagnetic gate due to its analogy to the alignment of molecular magnetic moments in a classical magnet. A high-fidelity Rydberg-mediated QFG can be realized in a time of with the maximal Rydberg Rabi frequency. From a product state of three data atoms and one ancilla atom, a gluing circuit with one QFG, two single-qubit gates, and a projective measurement of the ancilla can generate a 3-qubit GHZ state, and repetition of this gluing circuit can lead to 9, 27, 81, 243 -qubit GHZ states. Analyses based on currently available techniques show that a 243-qubit GHZ state is realizable, and more qubits can be entangled with higher detection fidelity.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"15 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056980","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 : 2026-01-28DOI: 10.1088/2058-9565/ae379d
Hiroyoshi Kurogi, Katsuhiro Endo, Yuki Sato, Michihiko Sugawara, Kaito Wada, Kenji Sugisaki, Shu Kanno, Hiroshi C Watanabe and Haruyuki Nakano
In variational quantum algorithms (VQAs), parameterization is typically applied to single-qubit gates. In this study, we instead parameterize a generalized controlled gate and propose an algorithm to locally minimize the cost function by maximally optimizing these parameters. This method extends the free quaternion selection technique, which was originally developed for single-qubit gate optimization. To evaluate its performance, we apply the proposed method to a variety of quantum optimization tasks, including the variational quantum eigensolver for both Ising and molecular Hamiltonians, fidelity maximization in general VQAs, and unitary compilation of time evolution operators. Across these applications, our method demonstrates efficient optimization, enhanced expressibility, and the ability to construct shallower circuits compared to existing techniques. Moreover, the method can be generalized to optimize particle-number-conserving gates, which are particularly relevant for quantum chemistry. Leveraging this capability, we further demonstrate that the method achieves superior quantum compilation of molecular time-evolution operators by approximating them with shallower circuits than standard Trotter decomposition.
{"title":"Optimizing a parameterized controlled gate using free quaternion selection","authors":"Hiroyoshi Kurogi, Katsuhiro Endo, Yuki Sato, Michihiko Sugawara, Kaito Wada, Kenji Sugisaki, Shu Kanno, Hiroshi C Watanabe and Haruyuki Nakano","doi":"10.1088/2058-9565/ae379d","DOIUrl":"https://doi.org/10.1088/2058-9565/ae379d","url":null,"abstract":"In variational quantum algorithms (VQAs), parameterization is typically applied to single-qubit gates. In this study, we instead parameterize a generalized controlled gate and propose an algorithm to locally minimize the cost function by maximally optimizing these parameters. This method extends the free quaternion selection technique, which was originally developed for single-qubit gate optimization. To evaluate its performance, we apply the proposed method to a variety of quantum optimization tasks, including the variational quantum eigensolver for both Ising and molecular Hamiltonians, fidelity maximization in general VQAs, and unitary compilation of time evolution operators. Across these applications, our method demonstrates efficient optimization, enhanced expressibility, and the ability to construct shallower circuits compared to existing techniques. Moreover, the method can be generalized to optimize particle-number-conserving gates, which are particularly relevant for quantum chemistry. Leveraging this capability, we further demonstrate that the method achieves superior quantum compilation of molecular time-evolution operators by approximating them with shallower circuits than standard Trotter decomposition.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"295 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056984","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 : 2026-01-28DOI: 10.1088/2058-9565/ae390d
Dávid Szász-Schagrin, Daniele Cristani, Lorenzo Piroli and Eric Vernier
We provide a systematic construction for local quantum circuits hosting free fermions in disguise (FFD), both with staircase and brickwork architectures. Similar to the original Hamiltonian model introduced by Fendley, these circuits are defined by the fact that the Floquet operator corresponding to a single time step can not be diagonalized by means of any Jordan–Wigner transformation, but still displays a free-fermionic spectrum. Our construction makes use of suitable non-local transfer matrices commuting with the Floquet operator, allowing us to establish the free fermionic spectrum. We also study the dynamics of these circuits after they are initialized in arbitrary product states, proving that the evolution of certain local observables can be simulated efficiently on classical computers. Our work proves recent conjectures in the literature and raises new questions on the classical simulability of FFD.
{"title":"Construction and simulability of quantum circuits with free fermions in disguise","authors":"Dávid Szász-Schagrin, Daniele Cristani, Lorenzo Piroli and Eric Vernier","doi":"10.1088/2058-9565/ae390d","DOIUrl":"https://doi.org/10.1088/2058-9565/ae390d","url":null,"abstract":"We provide a systematic construction for local quantum circuits hosting free fermions in disguise (FFD), both with staircase and brickwork architectures. Similar to the original Hamiltonian model introduced by Fendley, these circuits are defined by the fact that the Floquet operator corresponding to a single time step can not be diagonalized by means of any Jordan–Wigner transformation, but still displays a free-fermionic spectrum. Our construction makes use of suitable non-local transfer matrices commuting with the Floquet operator, allowing us to establish the free fermionic spectrum. We also study the dynamics of these circuits after they are initialized in arbitrary product states, proving that the evolution of certain local observables can be simulated efficiently on classical computers. Our work proves recent conjectures in the literature and raises new questions on the classical simulability of FFD.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"73 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056986","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 : 2026-01-28DOI: 10.1088/2058-9565/ae34e3
Mitchell J Walker, Ryuji Moriya, Jack D Segal, Liam A P Gallagher, Matthew Hill, Frédéric Leroux, Zhongxiao Xu and Matthew P A Jones
Arrays of neutral atoms in optical tweezers are widely used in quantum simulation and computation, and precision frequency metrology. The capabilities of these arrays are enhanced by maximising the number of available sites. Here we increase the spatial extent of a two-dimensional array of 88Sr atoms by sweeping the frequency of the cooling light to move the atomic reservoir across the array. We load arrays with vertical heights of 100 µm, exceeding the height of an array loaded from a static reservoir by a factor of 3. We investigate the site-to-site atom number distribution, tweezer lifetime, and temperature, achieving an average temperature across the array of µK. By controlling the frequency sweep we show it is possible to control the distribution of atoms across the array, including uniform and non-uniformly loaded arrays, and arrays with selectively loaded regions. We explain our results using a rate equation model which is in qualitative agreement with the data.
{"title":"Painted loading: a toolkit for loading spatially large optical tweezer arrays","authors":"Mitchell J Walker, Ryuji Moriya, Jack D Segal, Liam A P Gallagher, Matthew Hill, Frédéric Leroux, Zhongxiao Xu and Matthew P A Jones","doi":"10.1088/2058-9565/ae34e3","DOIUrl":"https://doi.org/10.1088/2058-9565/ae34e3","url":null,"abstract":"Arrays of neutral atoms in optical tweezers are widely used in quantum simulation and computation, and precision frequency metrology. The capabilities of these arrays are enhanced by maximising the number of available sites. Here we increase the spatial extent of a two-dimensional array of 88Sr atoms by sweeping the frequency of the cooling light to move the atomic reservoir across the array. We load arrays with vertical heights of 100 µm, exceeding the height of an array loaded from a static reservoir by a factor of 3. We investigate the site-to-site atom number distribution, tweezer lifetime, and temperature, achieving an average temperature across the array of µK. By controlling the frequency sweep we show it is possible to control the distribution of atoms across the array, including uniform and non-uniformly loaded arrays, and arrays with selectively loaded regions. We explain our results using a rate equation model which is in qualitative agreement with the data.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"42 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056982","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 : 2026-01-21DOI: 10.1088/2058-9565/ae36cd
Jaromír Fiurášek
Entanglement of continuous-variable Gaussian states can be distilled by combination of de-Gaussifying operation such as single-photon subtraction and iterative heralded Gaussification. Here we present and analyze a simplified equivalent version of such entanglement distillation protocol, where the Gaussian measurements utilized in heralded Gaussification are eliminated and are absorbed into the preparation of suitable input Gaussian states of the simplified protocol. The simplified scheme contains less detectors and its overall success probability increases in comparison with the original scheme, while producing completely equivalent outputs. Our simplification of the entanglement distillation protocol closely parallels the recently proposed simplification of a scheme for breeding optical single-mode Gottesman–Kitaev–Preskill states (Aghaee Rad et al 2025 Nature638 912 ). We investigate operation of the simplified entanglement distillation scheme for both pure and mixed input states and clarify how multicopy distillation of Gaussian entanglement emerges in a setup without any heralding Gaussian measurements.
结合单光子减法和迭代预传高斯化等反高斯化操作，可以提取连续变量高斯态的纠缠态。在这里，我们提出并分析了这种纠缠蒸馏协议的简化等效版本，其中消除了预先高斯化中使用的高斯测量值，并将其吸收到简化协议的合适输入高斯状态的准备中。简化方案包含较少的检测器，与原始方案相比，其总体成功概率增加，同时产生完全等效的输出。我们对纠缠蒸馏协议的简化与最近提出的光学单模Gottesman-Kitaev-Preskill态育种方案的简化非常相似（Aghaee Rad et al 2025 Nature638 912）。我们研究了纯输入态和混合输入态的简化纠缠蒸馏方案的操作，并阐明了在没有任何前兆高斯测量的情况下，高斯纠缠的多拷贝蒸馏是如何出现的。
{"title":"Simplified scheme for continuous-variable entanglement distillation: multicopy distillation of Gaussian entanglement without heralding Gaussian measurements","authors":"Jaromír Fiurášek","doi":"10.1088/2058-9565/ae36cd","DOIUrl":"https://doi.org/10.1088/2058-9565/ae36cd","url":null,"abstract":"Entanglement of continuous-variable Gaussian states can be distilled by combination of de-Gaussifying operation such as single-photon subtraction and iterative heralded Gaussification. Here we present and analyze a simplified equivalent version of such entanglement distillation protocol, where the Gaussian measurements utilized in heralded Gaussification are eliminated and are absorbed into the preparation of suitable input Gaussian states of the simplified protocol. The simplified scheme contains less detectors and its overall success probability increases in comparison with the original scheme, while producing completely equivalent outputs. Our simplification of the entanglement distillation protocol closely parallels the recently proposed simplification of a scheme for breeding optical single-mode Gottesman–Kitaev–Preskill states (Aghaee Rad et al 2025 Nature638 912 ). We investigate operation of the simplified entanglement distillation scheme for both pure and mixed input states and clarify how multicopy distillation of Gaussian entanglement emerges in a setup without any heralding Gaussian measurements.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006259","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 : 2026-01-20DOI: 10.1088/2058-9565/ae30a5
Liam Flannigan, Mostafa Khalil, Phyllis Chiu and Chang-qing Xu
Satellite quantum key distribution technology has developed rapidly using near-infrared wavelengths and is expected to enable global quantum communication. However, link availability is still hampered by detrimental effects in the free-space channel, such as background noise from solar radiation and attenuation from turbulence and weather such as haze and fog. One potential mitigation technique is to move to the mid-infrared atmospheric transmission window (3–5 µms) where background noise and turbulence effects are significantly reduced. While mid-infrared quantum technology is not as well developed, advancements in mid-infrared entangled photon pair generation and nonlinear upconversion single-photon detectors could be poised to enable daytime satellite downlinks with increased reliability. This review compares the state of the art for quantum transmitters and receivers in the mid-infrared to the more established near-infrared technology. The goal is to identify gaps in transmitter and/or receiver technology in the mid-infrared, and to determine if the mid-infrared can offer significant advantages over the near infrared for quantum communication.
{"title":"Recent progress on mid-infrared single-photon detectors and sources for satellite-based quantum key distribution—a review","authors":"Liam Flannigan, Mostafa Khalil, Phyllis Chiu and Chang-qing Xu","doi":"10.1088/2058-9565/ae30a5","DOIUrl":"https://doi.org/10.1088/2058-9565/ae30a5","url":null,"abstract":"Satellite quantum key distribution technology has developed rapidly using near-infrared wavelengths and is expected to enable global quantum communication. However, link availability is still hampered by detrimental effects in the free-space channel, such as background noise from solar radiation and attenuation from turbulence and weather such as haze and fog. One potential mitigation technique is to move to the mid-infrared atmospheric transmission window (3–5 µms) where background noise and turbulence effects are significantly reduced. While mid-infrared quantum technology is not as well developed, advancements in mid-infrared entangled photon pair generation and nonlinear upconversion single-photon detectors could be poised to enable daytime satellite downlinks with increased reliability. This review compares the state of the art for quantum transmitters and receivers in the mid-infrared to the more established near-infrared technology. The goal is to identify gaps in transmitter and/or receiver technology in the mid-infrared, and to determine if the mid-infrared can offer significant advantages over the near infrared for quantum communication.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"43 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146001631","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 : 2026-01-20DOI: 10.1088/2058-9565/ae24a6
Árpád Lukács, Róbert Trényi, Tamás Vértesi and Géza Tóth
We discuss efficient methods to optimize the metrological performance over local Hamiltonians in a bipartite quantum system. For a given quantum state, our methods find the best local Hamiltonian for which the state outperforms separable states the most from the point of view of quantum metrology. We show that this problem can be reduced to maximizing the quantum Fisher information over a certain set of Hamiltonians. We present the quantum Fisher information in a bilinear form and maximize it by an iterative see-saw method, in which each step is based on semidefinite programming. We also solve the problem with the method of moments that works very well for smaller systems. Our approach is one of the efficient methods that can be applied for an optimization of the unitary dynamics in quantum metrology, the other methods being, for example, machine learning, variational quantum circuits, or neural networks. The advantage of our method is the fast and robust convergence due to the simple mathematical structure of the approach. We also consider a number of other problems in quantum information theory that can be solved in a similar manner. For instance, we determine the bound entangled quantum states that maximally violate the computable cross norm-realignment criterion.
{"title":"Iterative optimization in quantum metrology and entanglement theory using semidefinite programming","authors":"Árpád Lukács, Róbert Trényi, Tamás Vértesi and Géza Tóth","doi":"10.1088/2058-9565/ae24a6","DOIUrl":"https://doi.org/10.1088/2058-9565/ae24a6","url":null,"abstract":"We discuss efficient methods to optimize the metrological performance over local Hamiltonians in a bipartite quantum system. For a given quantum state, our methods find the best local Hamiltonian for which the state outperforms separable states the most from the point of view of quantum metrology. We show that this problem can be reduced to maximizing the quantum Fisher information over a certain set of Hamiltonians. We present the quantum Fisher information in a bilinear form and maximize it by an iterative see-saw method, in which each step is based on semidefinite programming. We also solve the problem with the method of moments that works very well for smaller systems. Our approach is one of the efficient methods that can be applied for an optimization of the unitary dynamics in quantum metrology, the other methods being, for example, machine learning, variational quantum circuits, or neural networks. The advantage of our method is the fast and robust convergence due to the simple mathematical structure of the approach. We also consider a number of other problems in quantum information theory that can be solved in a similar manner. For instance, we determine the bound entangled quantum states that maximally violate the computable cross norm-realignment criterion.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"60 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000780","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 : 2026-01-19DOI: 10.1088/2058-9565/ae34e2
Himanshu Badhani, Dhanuja GS, Swati Choudhary, Vishal Anand and Siddhartha Das
The erasure of information is fundamentally an irreversible logical operation, carrying profound consequences for the energetics of computation and information processing. We investigate the thermodynamic costs associated with erasing (and preparing) quantum processes. Specifically, we analyze an arbitrary bipartite unitary gate acting on logical and ancillary input-output systems, where the ancillary input is always initialized in the ground state. We focus on the adversarial erasure cost of the reduced dynamics—that is, the minimal thermodynamic work cost to erase the logical output of the gate for any logical input, assuming full access to the ancilla but no access to any purifying reference of the logical input state. We determine that this adversarial erasure cost is directly proportional to the negative min-entropy of the reduced dynamics, thereby giving the dynamical min-entropy a clear operational meaning. The dynamical min-entropy can take positive and negative values, depending on the underlying quantum dynamics. The negative value of the erasure cost implies that the extraction of thermodynamic work is possible instead of its consumption during the process. A key foundation of this result is the quantum process decoupling theorem, which quantitatively relates the decoupling ability of a process with its min-entropy. This insight bridges thermodynamics, information theory, and the fundamental limits of quantum computation.
{"title":"Erasure cost of a quantum process: a thermodynamic meaning of the dynamical min-entropy","authors":"Himanshu Badhani, Dhanuja GS, Swati Choudhary, Vishal Anand and Siddhartha Das","doi":"10.1088/2058-9565/ae34e2","DOIUrl":"https://doi.org/10.1088/2058-9565/ae34e2","url":null,"abstract":"The erasure of information is fundamentally an irreversible logical operation, carrying profound consequences for the energetics of computation and information processing. We investigate the thermodynamic costs associated with erasing (and preparing) quantum processes. Specifically, we analyze an arbitrary bipartite unitary gate acting on logical and ancillary input-output systems, where the ancillary input is always initialized in the ground state. We focus on the adversarial erasure cost of the reduced dynamics—that is, the minimal thermodynamic work cost to erase the logical output of the gate for any logical input, assuming full access to the ancilla but no access to any purifying reference of the logical input state. We determine that this adversarial erasure cost is directly proportional to the negative min-entropy of the reduced dynamics, thereby giving the dynamical min-entropy a clear operational meaning. The dynamical min-entropy can take positive and negative values, depending on the underlying quantum dynamics. The negative value of the erasure cost implies that the extraction of thermodynamic work is possible instead of its consumption during the process. A key foundation of this result is the quantum process decoupling theorem, which quantitatively relates the decoupling ability of a process with its min-entropy. This insight bridges thermodynamics, information theory, and the fundamental limits of quantum computation.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"26 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995425","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 : 2026-01-19DOI: 10.1088/2058-9565/ae3551
Félix Hoffet, Alexey Vylegzhanin, Emanuele Distante, Lukas Heller, Síle Nic Chormaic and Hugues de Riedmatten
A promising platform for quantum information research relies on cavity coupled atomic spin-waves, enabling efficient operations such as quantum memories, quantum light generation and entanglement distribution. In this work, we study the strong coupling between non-classical collective spin excitations generated by Raman scattering in a cold atomic ensemble, and a single cavity mode. We report on an intracavity spin wave to single photon conversion efficiency of up to in the quantum domain, as evidenced by a violation of the Cauchy–Schwarz inequality. Our work establishes a relationship between the retrieval of an atomic spin wave in the non-classical regime and the vacuum Rabi splitting. We show that this relationship emerges within the efficiency spectrum, and we finally provide the optimal operational conditions to achieve the maximum intrinsic retrieval efficiency. Our data is well reproduced by simulations based on optical Bloch equations. This work deepens the understanding of cavity-enhanced spin wave readout and its potential applications.
{"title":"Collective vacuum Rabi splitting with an atomic spin wave coupled to a cavity mode","authors":"Félix Hoffet, Alexey Vylegzhanin, Emanuele Distante, Lukas Heller, Síle Nic Chormaic and Hugues de Riedmatten","doi":"10.1088/2058-9565/ae3551","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3551","url":null,"abstract":"A promising platform for quantum information research relies on cavity coupled atomic spin-waves, enabling efficient operations such as quantum memories, quantum light generation and entanglement distribution. In this work, we study the strong coupling between non-classical collective spin excitations generated by Raman scattering in a cold atomic ensemble, and a single cavity mode. We report on an intracavity spin wave to single photon conversion efficiency of up to in the quantum domain, as evidenced by a violation of the Cauchy–Schwarz inequality. Our work establishes a relationship between the retrieval of an atomic spin wave in the non-classical regime and the vacuum Rabi splitting. We show that this relationship emerges within the efficiency spectrum, and we finally provide the optimal operational conditions to achieve the maximum intrinsic retrieval efficiency. Our data is well reproduced by simulations based on optical Bloch equations. This work deepens the understanding of cavity-enhanced spin wave readout and its potential applications.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"24 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995426","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 : 2026-01-16DOI: 10.1088/2058-9565/ae3029
Alejandro Villoria, Henning Basold and Alfons Laarman
Compiling quantum circuits to account for hardware restrictions is an essential part of the quantum computing stack. Circuit compilation allows us to adapt algorithm descriptions into a sequence of operations supported by real quantum hardware, and has the potential to significantly improve their performance when optimisation techniques are added to the process. One such optimisation technique is reducing the number of quantum gates that are needed to execute a circuit. For instance, methods for reducing the number of non-Clifford gates or CNOT gates from a circuit are an extensive research area that has gathered significant interest over the years. For certain hardware platforms such as trapped-ion quantum computers, we can leverage some of their special properties to further reduce the cost of executing a quantum circuit in them. In this work we use global interactions, such as the Global Mølmer–Sørensen (MS) gate present in trapped-ion hardware, to optimise and synthesise quantum circuits. We design and implement an algorithm that is able to compile an arbitrary quantum circuit into another circuit that uses global gates as the entangling operation, while optimising the number of global interactions needed. The algorithm is based on the ZX-calculus and uses a specialised circuit extraction routine that groups entangling gates into Global MS gates. We benchmark the algorithm in a variety of circuits, and show how it improves their performance under state-of-the-art hardware considerations in comparison to a naive algorithm and the Qiskit optimiser.
{"title":"Optimisation and synthesis of quantum circuits with global gates","authors":"Alejandro Villoria, Henning Basold and Alfons Laarman","doi":"10.1088/2058-9565/ae3029","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3029","url":null,"abstract":"Compiling quantum circuits to account for hardware restrictions is an essential part of the quantum computing stack. Circuit compilation allows us to adapt algorithm descriptions into a sequence of operations supported by real quantum hardware, and has the potential to significantly improve their performance when optimisation techniques are added to the process. One such optimisation technique is reducing the number of quantum gates that are needed to execute a circuit. For instance, methods for reducing the number of non-Clifford gates or CNOT gates from a circuit are an extensive research area that has gathered significant interest over the years. For certain hardware platforms such as trapped-ion quantum computers, we can leverage some of their special properties to further reduce the cost of executing a quantum circuit in them. In this work we use global interactions, such as the Global Mølmer–Sørensen (MS) gate present in trapped-ion hardware, to optimise and synthesise quantum circuits. We design and implement an algorithm that is able to compile an arbitrary quantum circuit into another circuit that uses global gates as the entangling operation, while optimising the number of global interactions needed. The algorithm is based on the ZX-calculus and uses a specialised circuit extraction routine that groups entangling gates into Global MS gates. We benchmark the algorithm in a variety of circuits, and show how it improves their performance under state-of-the-art hardware considerations in comparison to a naive algorithm and the Qiskit optimiser.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"41 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972324","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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