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}
Pub Date : 2025-11-13DOI: 10.1038/s41534-025-01138-2
Ruoming Peng, Xuntao Wu, Yang Wang, Jixing Zhang, Jianpei Geng, Durga Bhaktavatsala Rao Dasari, Andrew N. Cleland, Jörg Wrachtrup
Solid-state spins are promising for quantum information processing and networks, but their inhomogeneity hinders scalable control and entanglement. We propose a hybrid spin-phonon architecture based on spin-embedded SiC optomechanical crystal (OMC) cavities, which integrate photonic and phononic channels for multi-spin interactions. Using a Raman-facilitated process, spins strongly couple to the OMC cavity’s zero-point motion at 0.57 MHz, enabling coherent spin-phonon interactions. This interface supports a two-qubit controlled-Z gate with simulated fidelity of 96.80% and efficiently generates entangled Dicke states with over 99% fidelity by leveraging a robust spin-phonon dark state resilient to spectral inhomogeneity and excited-state loss. The platform offers potential scalability and all-to-all connectivity via phonons, along with optical links, enabling both entanglement generation and quantum acoustics studies in the solid state.
{"title":"Hybrid spin-phonon architecture for scalable solid-state quantum nodes","authors":"Ruoming Peng, Xuntao Wu, Yang Wang, Jixing Zhang, Jianpei Geng, Durga Bhaktavatsala Rao Dasari, Andrew N. Cleland, Jörg Wrachtrup","doi":"10.1038/s41534-025-01138-2","DOIUrl":"https://doi.org/10.1038/s41534-025-01138-2","url":null,"abstract":"Solid-state spins are promising for quantum information processing and networks, but their inhomogeneity hinders scalable control and entanglement. We propose a hybrid spin-phonon architecture based on spin-embedded SiC optomechanical crystal (OMC) cavities, which integrate photonic and phononic channels for multi-spin interactions. Using a Raman-facilitated process, spins strongly couple to the OMC cavity’s zero-point motion at 0.57 MHz, enabling coherent spin-phonon interactions. This interface supports a two-qubit controlled-Z gate with simulated fidelity of 96.80% and efficiently generates entangled Dicke states with over 99% fidelity by leveraging a robust spin-phonon dark state resilient to spectral inhomogeneity and excited-state loss. The platform offers potential scalability and all-to-all connectivity via phonons, along with optical links, enabling both entanglement generation and quantum acoustics studies in the solid state.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"38 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145509012","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 : 2025-11-10DOI: 10.1038/s41534-025-01112-y
Simone Cavazzoni, Berihu Teklu, Matteo G. A. Paris
{"title":"Frequency estimation by frequency jumps","authors":"Simone Cavazzoni, Berihu Teklu, Matteo G. A. Paris","doi":"10.1038/s41534-025-01112-y","DOIUrl":"https://doi.org/10.1038/s41534-025-01112-y","url":null,"abstract":"","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"22 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145477984","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 : 2025-11-07DOI: 10.1038/s41534-025-01111-z
Eugenio Caruccio, Diego Maragnano, Giovanni Rodari, Davide Picus, Giovanni Garberoglio, Daniele Binosi, Riccardo Albiero, Niki Di Giano, Francesco Ceccarelli, Giacomo Corrielli, Nicolò Spagnolo, Roberto Osellame, Maurizio Dapor, Marco Liscidini, Fabio Sciarrino
Reconstructing the state of a quantum system represents a pivotal task for quantum information applications. The standard approach based on quantum state tomography requires a number of measurements that scales exponentially with the number of qubits. Other methods have been proposed and tested to reduce the number of measurements, or to focus on specific properties of the output state rather than on its complete reconstruction. Here, we show experimentally the application of an approach, called threshold quantum state tomography, in an advanced hybrid photonic platform with states up to n = 4 qubits. This method does not require prior knowledge and selects only the informative projectors starting from the measurement of the density matrix diagonal. We demonstrate its effectiveness by showing that a consistent reduction in the number of measurements is obtained for relevant states, with only very limited loss of information. These results open perspective for its application in larger systems.
{"title":"Experimental verification of threshold quantum state tomography on a fully-reconfigurable photonic integrated circuit","authors":"Eugenio Caruccio, Diego Maragnano, Giovanni Rodari, Davide Picus, Giovanni Garberoglio, Daniele Binosi, Riccardo Albiero, Niki Di Giano, Francesco Ceccarelli, Giacomo Corrielli, Nicolò Spagnolo, Roberto Osellame, Maurizio Dapor, Marco Liscidini, Fabio Sciarrino","doi":"10.1038/s41534-025-01111-z","DOIUrl":"https://doi.org/10.1038/s41534-025-01111-z","url":null,"abstract":"Reconstructing the state of a quantum system represents a pivotal task for quantum information applications. The standard approach based on quantum state tomography requires a number of measurements that scales exponentially with the number of qubits. Other methods have been proposed and tested to reduce the number of measurements, or to focus on specific properties of the output state rather than on its complete reconstruction. Here, we show experimentally the application of an approach, called threshold quantum state tomography, in an advanced hybrid photonic platform with states up to <jats:italic>n</jats:italic> = 4 qubits. This method does not require prior knowledge and selects only the informative projectors starting from the measurement of the density matrix diagonal. We demonstrate its effectiveness by showing that a consistent reduction in the number of measurements is obtained for relevant states, with only very limited loss of information. These results open perspective for its application in larger systems.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"49 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145455636","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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