Pub Date : 2025-11-25DOI: 10.1038/s41534-025-01128-4
Oskar Leimkuhler, K. Birgitta Whaley
Electronic ground states are of central importance in chemical simulations, but have remained beyond the reach of efficient classical algorithms except in cases of weak electron correlation or one-dimensional spatial geometry. We introduce a hybrid quantum-classical eigenvalue solver that constructs a wavefunction ansatz from a linear combination of matrix product states in rotated orbital bases, enabling the characterization of strongly correlated ground states with arbitrary spatial geometry. The energy is converged via a gradient-free generalized sweep algorithm based on quantum subspace diagonalization, with a potentially exponential speedup in the off-diagonal matrix element contractions upon translation into compact quantum circuits of linear depth in the number of qubits. Chemical accuracy is attained in numerical experiments for both a stretched water molecule and an octahedral arrangement of hydrogen atoms, achieving substantially better correlation energies compared to a unitary coupled-cluster benchmark, with orders of magnitude reductions in quantum resource estimates and a surprisingly high tolerance to shot noise. This proof-of-concept study suggests a promising new avenue for scaling up simulations of strongly correlated chemical systems on near-term quantum hardware.
{"title":"A quantum eigenvalue solver based on tensor networks","authors":"Oskar Leimkuhler, K. Birgitta Whaley","doi":"10.1038/s41534-025-01128-4","DOIUrl":"https://doi.org/10.1038/s41534-025-01128-4","url":null,"abstract":"Electronic ground states are of central importance in chemical simulations, but have remained beyond the reach of efficient classical algorithms except in cases of weak electron correlation or one-dimensional spatial geometry. We introduce a hybrid quantum-classical eigenvalue solver that constructs a wavefunction ansatz from a linear combination of matrix product states in rotated orbital bases, enabling the characterization of strongly correlated ground states with arbitrary spatial geometry. The energy is converged via a gradient-free generalized sweep algorithm based on quantum subspace diagonalization, with a potentially exponential speedup in the off-diagonal matrix element contractions upon translation into compact quantum circuits of linear depth in the number of qubits. Chemical accuracy is attained in numerical experiments for both a stretched water molecule and an octahedral arrangement of hydrogen atoms, achieving substantially better correlation energies compared to a unitary coupled-cluster benchmark, with orders of magnitude reductions in quantum resource estimates and a surprisingly high tolerance to shot noise. This proof-of-concept study suggests a promising new avenue for scaling up simulations of strongly correlated chemical systems on near-term quantum hardware.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"17 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593349","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 : 2025-11-25DOI: 10.1038/s41534-025-01145-3
Guorui Zhu, Joel Bierman, Jianfeng Lu, Yingzhou Li
{"title":"Quantum circuit for non-unitary linear transformation of basis sets","authors":"Guorui Zhu, Joel Bierman, Jianfeng Lu, Yingzhou Li","doi":"10.1038/s41534-025-01145-3","DOIUrl":"https://doi.org/10.1038/s41534-025-01145-3","url":null,"abstract":"","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"163 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593350","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 : 2025-11-21DOI: 10.1038/s41534-025-01143-5
I. Arrazola, P. Bertet, Y. Chu, P. Rabl
We study a generic cavity QED setup under conditions where the coupling between the two-level systems and a single bosonic mode is significantly degraded by low-frequency noise. To overcome this problem, we identify pulsed dynamical decoupling strategies that suppress the effects of noise while still allowing for a coherent exchange of excitations between the individual subsystems. The corresponding pulse sequences can be further designed to realize either Jaynes-Cummings, anti-Jaynes-Cummings, or Rabi couplings, as well as different types of cavity-mediated interactions between the two-level systems. A detailed analysis of the residual imperfections demonstrates that this decoupling strategy can boost the effective cooperativity of the cavity QED system by several orders of magnitude and improve the fidelity of quantum-technologically relevant operations accordingly.
{"title":"Engineering protected cavity-QED interactions through pulsed dynamical decoupling","authors":"I. Arrazola, P. Bertet, Y. Chu, P. Rabl","doi":"10.1038/s41534-025-01143-5","DOIUrl":"https://doi.org/10.1038/s41534-025-01143-5","url":null,"abstract":"We study a generic cavity QED setup under conditions where the coupling between the two-level systems and a single bosonic mode is significantly degraded by low-frequency noise. To overcome this problem, we identify pulsed dynamical decoupling strategies that suppress the effects of noise while still allowing for a coherent exchange of excitations between the individual subsystems. The corresponding pulse sequences can be further designed to realize either Jaynes-Cummings, anti-Jaynes-Cummings, or Rabi couplings, as well as different types of cavity-mediated interactions between the two-level systems. A detailed analysis of the residual imperfections demonstrates that this decoupling strategy can boost the effective cooperativity of the cavity QED system by several orders of magnitude and improve the fidelity of quantum-technologically relevant operations accordingly.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"9 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145559874","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 : 2025-11-20DOI: 10.1038/s41534-025-01119-5
Fenglei Gu, Shankar G. Menon, David Maier, Antariksha Das, Tanmoy Chakraborty, Wolfgang Tittel, Hannes Bernien, Johannes Borregaard
{"title":"Hybrid quantum repeaters with ensemble-based quantum memories and single-spin photon transducers","authors":"Fenglei Gu, Shankar G. Menon, David Maier, Antariksha Das, Tanmoy Chakraborty, Wolfgang Tittel, Hannes Bernien, Johannes Borregaard","doi":"10.1038/s41534-025-01119-5","DOIUrl":"https://doi.org/10.1038/s41534-025-01119-5","url":null,"abstract":"","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"165 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145554226","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 : 2025-11-20DOI: 10.1038/s41534-025-01124-8
Hao-En Li, Yongtao Zhan, Lin Lin
Dissipative engineering is a powerful tool for quantum state preparation, and has drawn significant attention in quantum algorithms and quantum many-body physics in recent years. In this work, we introduce a novel approach using the Lindblad dynamics to efficiently prepare the ground state for general ab initio electronic structure problems on quantum computers, without variational parameters. These problems often involve Hamiltonians that lack geometric locality or sparsity structures, which we address by proposing two generic types of jump operators for the Lindblad dynamics. Type-I jump operators break the particle number symmetry and should be simulated in the Fock space. Type-II jump operators preserves the particle number symmetry and can be simulated more efficiently in the full configuration interaction space. For both types of jump operators, we prove that in a simplified Hartree-Fock framework, the spectral gap of our Lindbladian is lower bounded by a universal constant. For physical observables such as energy and reduced density matrices, the convergence rate of our Lindblad dynamics with Type-I jump operators remains universal, while the convergence rate with Type-II jump operators only depends on coarse grained information such as the number of orbitals and the number of electrons. To validate our approach, we employ a Monte Carlo trajectory-based algorithm for simulating the Lindblad dynamics for full ab initio Hamiltonians, demonstrating its effectiveness on molecular systems amenable to exact wavefunction treatment.
{"title":"Dissipative ground state preparation in ab initio electronic structure theory","authors":"Hao-En Li, Yongtao Zhan, Lin Lin","doi":"10.1038/s41534-025-01124-8","DOIUrl":"https://doi.org/10.1038/s41534-025-01124-8","url":null,"abstract":"Dissipative engineering is a powerful tool for quantum state preparation, and has drawn significant attention in quantum algorithms and quantum many-body physics in recent years. In this work, we introduce a novel approach using the Lindblad dynamics to efficiently prepare the ground state for general ab initio electronic structure problems on quantum computers, without variational parameters. These problems often involve Hamiltonians that lack geometric locality or sparsity structures, which we address by proposing two generic types of jump operators for the Lindblad dynamics. Type-I jump operators break the particle number symmetry and should be simulated in the Fock space. Type-II jump operators preserves the particle number symmetry and can be simulated more efficiently in the full configuration interaction space. For both types of jump operators, we prove that in a simplified Hartree-Fock framework, the spectral gap of our Lindbladian is lower bounded by a <jats:italic>universal</jats:italic> constant. For physical observables such as energy and reduced density matrices, the convergence rate of our Lindblad dynamics with Type-I jump operators remains universal, while the convergence rate with Type-II jump operators only depends on coarse grained information such as the number of orbitals and the number of electrons. To validate our approach, we employ a Monte Carlo trajectory-based algorithm for simulating the Lindblad dynamics for full ab initio Hamiltonians, demonstrating its effectiveness on molecular systems amenable to exact wavefunction treatment.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"1 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145554228","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 : 2025-11-19DOI: 10.1038/s41534-025-01120-y
Jasmin Bedow, Dirk K. Morr
{"title":"Solving the Bernstein-Vazirani problem using Majorana-based topological quantum algorithms","authors":"Jasmin Bedow, Dirk K. Morr","doi":"10.1038/s41534-025-01120-y","DOIUrl":"https://doi.org/10.1038/s41534-025-01120-y","url":null,"abstract":"","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"275 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145545450","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 : 2025-11-19DOI: 10.1038/s41534-025-01125-7
Marcus J. Clark, Obada Alia, Sima Bahrani, Gregory T. Jasion, Hesham Sakr, Periklis Petropoulos, Francesco Poletti, George T. Kanellos, John Rarity, Reza Nejabati, Siddarth K. Joshi, Rui Wang, Dimitra Simeonidou
We experimentally demonstrate the coexistence of three entanglement-based quantum channels with carrier-grade classical optical channels over 11.5 km hollow core nested antiresonant nodeless fibre, in a four user quantum network. A transmission of 800 Gbps is achieved with four classical channels simultaneously with three quantum channels all operating in the C-band with a separation of 1.2 nm, with aggregated coexistence power of −3 dBm. We established quantum key distribution in the four-node full-mesh quantum network with Bell state fidelity of up to 90.0 ± 0.8%. The secret key rate for all the links in the network are passively preserved over 55 hours of experimental time.
{"title":"Coexistence of entanglement-based quantum channels with DWDM classical channels over hollow core fibre in a four node quantum communication network","authors":"Marcus J. Clark, Obada Alia, Sima Bahrani, Gregory T. Jasion, Hesham Sakr, Periklis Petropoulos, Francesco Poletti, George T. Kanellos, John Rarity, Reza Nejabati, Siddarth K. Joshi, Rui Wang, Dimitra Simeonidou","doi":"10.1038/s41534-025-01125-7","DOIUrl":"https://doi.org/10.1038/s41534-025-01125-7","url":null,"abstract":"We experimentally demonstrate the coexistence of three entanglement-based quantum channels with carrier-grade classical optical channels over 11.5 km hollow core nested antiresonant nodeless fibre, in a four user quantum network. A transmission of 800 Gbps is achieved with four classical channels simultaneously with three quantum channels all operating in the C-band with a separation of 1.2 nm, with aggregated coexistence power of −3 dBm. We established quantum key distribution in the four-node full-mesh quantum network with Bell state fidelity of up to 90.0 ± 0.8%. The secret key rate for all the links in the network are passively preserved over 55 hours of experimental time.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"97 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145554229","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 : 2025-11-18DOI: 10.1038/s41534-025-01121-x
Kevin Shen, Andrii Kurkin, Adrián Pérez-Salinas, Elvira Shishenina, Vedran Dunjko, Hao Wang
Expectation Value Samplers (EVSs) are quantum generative models that can learn high-dimensional continuous distributions by measuring the expectation values of parameterized quantum circuits. However, these models can demand impractical quantum resources for good performance. We investigate how observable choices affect EVS performance and propose an Observable-Tunable Expectation Value Sampler (OT-EVS), which achieves greater expressivity than standard EVS. By restricting the selectable observables, it is possible to use the classical shadows measurement scheme to reduce the sample complexity of our algorithm. In addition, we propose an adversarial training method adapted to the needs of OT-EVS. This training prioritizes classical updates of observables, minimizing the more costly updates of quantum circuit parameters. Numerical experiments, using an original simulation technique for correlated shot noise, confirm our model’s expressivity and sample efficiency advantages compared to previous designs. We envision our proposal to encourage the exploration of continuous generative models running with few quantum resources.
{"title":"Variational quantum generative modeling by sampling expectation values of tunable observables","authors":"Kevin Shen, Andrii Kurkin, Adrián Pérez-Salinas, Elvira Shishenina, Vedran Dunjko, Hao Wang","doi":"10.1038/s41534-025-01121-x","DOIUrl":"https://doi.org/10.1038/s41534-025-01121-x","url":null,"abstract":"Expectation Value Samplers (EVSs) are quantum generative models that can learn high-dimensional continuous distributions by measuring the expectation values of parameterized quantum circuits. However, these models can demand impractical quantum resources for good performance. We investigate how observable choices affect EVS performance and propose an Observable-Tunable Expectation Value Sampler (OT-EVS), which achieves greater expressivity than standard EVS. By restricting the selectable observables, it is possible to use the classical shadows measurement scheme to reduce the sample complexity of our algorithm. In addition, we propose an adversarial training method adapted to the needs of OT-EVS. This training prioritizes classical updates of observables, minimizing the more costly updates of quantum circuit parameters. Numerical experiments, using an original simulation technique for correlated shot noise, confirm our model’s expressivity and sample efficiency advantages compared to previous designs. We envision our proposal to encourage the exploration of continuous generative models running with few quantum resources.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"224 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145536101","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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