Pub Date : 2023-07-12DOI: 10.1140/epjqt/s40507-023-00185-y
Federico Berra, Costantino Agnesi, Andrea Stanco, Marco Avesani, Sebastiano Cocchi, Paolo Villoresi, Giuseppe Vallone
We present a source of states for Quantum Key Distribution (QKD) based on a modular design exploiting the iPOGNAC, a stable, low-error, and calibration-free polarization modulation scheme, for both intensity and polarization encoding. This source is immune to the security vulnerabilities of other state sources such as side channels and some quantum hacking attacks. Remarkably, our intensity modulation scheme allows full tunability of the intensity ratio between the decoy and signal states, and mitigates patterning effects. The source was implemented and tested at the near-infrared optical band around 800 nm, of particular interest for satellite-based QKD. Furthermore, the modularity of the source simplifies its development, testing, and qualification, especially for space missions. For these reasons, our work paves the way for the development of the second generation of QKD satellites that can guarantee excellent performances at higher security levels.
{"title":"Modular source for near-infrared quantum communication","authors":"Federico Berra, Costantino Agnesi, Andrea Stanco, Marco Avesani, Sebastiano Cocchi, Paolo Villoresi, Giuseppe Vallone","doi":"10.1140/epjqt/s40507-023-00185-y","DOIUrl":"10.1140/epjqt/s40507-023-00185-y","url":null,"abstract":"<div><p>We present a source of states for Quantum Key Distribution (QKD) based on a modular design exploiting the iPOGNAC, a stable, low-error, and calibration-free polarization modulation scheme, for both intensity and polarization encoding. This source is immune to the security vulnerabilities of other state sources such as side channels and some quantum hacking attacks. Remarkably, our intensity modulation scheme allows full tunability of the intensity ratio between the decoy and signal states, and mitigates patterning effects. The source was implemented and tested at the near-infrared optical band around 800 nm, of particular interest for satellite-based QKD. Furthermore, the modularity of the source simplifies its development, testing, and qualification, especially for space missions. For these reasons, our work paves the way for the development of the second generation of QKD satellites that can guarantee excellent performances at higher security levels.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00185-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4499981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-29DOI: 10.1140/epjqt/s40507-023-00183-0
Randy Kuang, Adrian Chan
In photonic computing, the quantum systems consist of coherent states and squeezed coherent states. Common quantum gates found in these systems are: phase shift, displacement, and squeezing gates. These gates are all unitary and reversible. Outside of quantum systems, coherent states also plays a significant role in coherent optical communications with speeds of hundreds of gigabits per second. Secure optical communications is generally implemented at the data layer with classical symmetric encryption such as Advanced Standard Encryption or AES. This inevitably allows any wiretapping to capture the transmitted data either in the plaintext mode or in the encrypted ciphertext mode in the optical infrastructure. The recent and rapid developments in Quantum computing further lift up the need for quantum secure communications in the optical infrastructure. This paper proposes a novel quantum encryption in the coherent optical domain utilizing a displacement operator and implementing with IQ-MZM optical modules, called Quantum Encryption in Phase Space or QEPS. The communication peers share a secret used to seed cryptographic pseudo random number generators to produce a synchronized random number at both the transmitter and receiver. The synchronized random numbers are used to establish displacement operators to encrypt the coherent states at the transmission and decrypt the cipher coherent states at the receiver. Therefore, malicious parties tapping along the fibre line would not extract the message in transit from optical domain due to a high Bit Error Rate or BER. The optimal displacement operator is split into a standard 16-QAM and a random phase shift operator to enhance the transmission security. We analysis the transmission security with the wiretap channel model for semantic security. We have simulated the QEPS encryption and decryption for two data modulation schemes: QPSK and 16-QAM over 80 km for transmission speeds of 56 Gbps for QPSK and 112 Gbps for 16-QAM.
{"title":"Quantum encryption in phase space with displacement operators","authors":"Randy Kuang, Adrian Chan","doi":"10.1140/epjqt/s40507-023-00183-0","DOIUrl":"10.1140/epjqt/s40507-023-00183-0","url":null,"abstract":"<div><p>In photonic computing, the quantum systems consist of coherent states and squeezed coherent states. Common quantum gates found in these systems are: phase shift, displacement, and squeezing gates. These gates are all unitary and reversible. Outside of quantum systems, coherent states also plays a significant role in coherent optical communications with speeds of hundreds of gigabits per second. Secure optical communications is generally implemented at the data layer with classical symmetric encryption such as Advanced Standard Encryption or AES. This inevitably allows any wiretapping to capture the transmitted data either in the plaintext mode or in the encrypted ciphertext mode in the optical infrastructure. The recent and rapid developments in Quantum computing further lift up the need for quantum secure communications in the optical infrastructure. This paper proposes a novel quantum encryption in the coherent optical domain utilizing a displacement operator and implementing with IQ-MZM optical modules, called Quantum Encryption in Phase Space or QEPS. The communication peers share a secret used to seed cryptographic pseudo random number generators to produce a synchronized random number at both the transmitter and receiver. The synchronized random numbers are used to establish displacement operators to encrypt the coherent states at the transmission and decrypt the cipher coherent states at the receiver. Therefore, malicious parties tapping along the fibre line would not extract the message in transit from optical domain due to a high Bit Error Rate or BER. The optimal displacement operator is split into a standard 16-QAM and a random phase shift operator to enhance the transmission security. We analysis the transmission security with the wiretap channel model for semantic security. We have simulated the QEPS encryption and decryption for two data modulation schemes: QPSK and 16-QAM over 80 km for transmission speeds of 56 Gbps for QPSK and 112 Gbps for 16-QAM.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00183-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5119462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-28DOI: 10.1140/epjqt/s40507-023-00181-2
Violeta N. Ivanova-Rohling, Niklas Rohling, Guido Burkard
Quantum state tomography (QST) represents an essential tool for the characterization, verification, and validation (QCVV) of quantum processors. Only for a few idealized scenarios, there are analytic results for the optimal measurement set for QST. E.g., in a setting of non-degenerate measurements, an optimal minimal set of measurement operators for QST has eigenbases which are mutually unbiased. However, in other set-ups, dependent on the rank of the projection operators and the size of the quantum system, the optimal choice of measurements for efficient QST needs to be numerically approximated. We have generalized this problem by introducing the framework of customized efficient QST. Here we extend customized QST and look for the optimal measurement set for QST in the case where some of the quantum gates applied in the measurement process are noisy. To achieve this, we use two distinct noise models: first, the depolarizing channel, and second, over- and under-rotation in single-qubit and to two-qubit gates (for further information, please see Methods). We demonstrate the benefit of using entangling gates for the efficient QST measurement schemes for two qubits at realistic noise levels, by comparing the fidelity of reconstruction of our optimized QST measurement set to the state-of-the-art scheme using only product bases.
{"title":"Optimal quantum state tomography with noisy gates","authors":"Violeta N. Ivanova-Rohling, Niklas Rohling, Guido Burkard","doi":"10.1140/epjqt/s40507-023-00181-2","DOIUrl":"10.1140/epjqt/s40507-023-00181-2","url":null,"abstract":"<div><p>Quantum state tomography (QST) represents an essential tool for the characterization, verification, and validation (QCVV) of quantum processors. Only for a few idealized scenarios, there are analytic results for the optimal measurement set for QST. E.g., in a setting of non-degenerate measurements, an optimal minimal set of measurement operators for QST has eigenbases which are mutually unbiased. However, in other set-ups, dependent on the rank of the projection operators and the size of the quantum system, the optimal choice of measurements for efficient QST needs to be numerically approximated. We have generalized this problem by introducing the framework of <i>customized efficient QST</i>. Here we extend customized QST and look for the optimal measurement set for QST in the case where some of the quantum gates applied in the measurement process are noisy. To achieve this, we use two distinct noise models: first, the depolarizing channel, and second, over- and under-rotation in single-qubit and to two-qubit gates (for further information, please see Methods). We demonstrate the benefit of using entangling gates for the efficient QST measurement schemes for two qubits at realistic noise levels, by comparing the fidelity of reconstruction of our optimized QST measurement set to the state-of-the-art scheme using only product bases.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00181-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5090538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-27DOI: 10.1140/epjqt/s40507-023-00182-1
Yan-Yan Hou, Jian Li, Xiu-Bo Chen, Chong-Qiang Ye
Metric learning plays an essential role in image analysis and classification, and it has attracted more and more attention. In this paper, we propose a quantum adversarial metric learning (QAML) model based on the triplet loss function, where samples are embedded into the high-dimensional Hilbert space and the optimal metric is obtained by minimizing the triplet loss function. The QAML model employs entanglement and interference to build superposition states for triplet samples so that only one parameterized quantum circuit is needed to calculate sample distances, which reduces the demand for quantum resources. Considering the QAML model is fragile to adversarial attacks, an adversarial sample generation strategy is designed based on the quantum gradient ascent method, effectively improving the robustness against the functional adversarial attack. Simulation results show that the QAML model can effectively distinguish samples of MNIST and Iris datasets and has higher ϵ-robustness accuracy over the general quantum metric learning. The QAML model is a fundamental research problem of machine learning. As a subroutine of classification and clustering tasks, the QAML model opens an avenue for exploring quantum advantages in machine learning.
{"title":"Quantum adversarial metric learning model based on triplet loss function","authors":"Yan-Yan Hou, Jian Li, Xiu-Bo Chen, Chong-Qiang Ye","doi":"10.1140/epjqt/s40507-023-00182-1","DOIUrl":"10.1140/epjqt/s40507-023-00182-1","url":null,"abstract":"<div><p>Metric learning plays an essential role in image analysis and classification, and it has attracted more and more attention. In this paper, we propose a quantum adversarial metric learning (QAML) model based on the triplet loss function, where samples are embedded into the high-dimensional Hilbert space and the optimal metric is obtained by minimizing the triplet loss function. The QAML model employs entanglement and interference to build superposition states for triplet samples so that only one parameterized quantum circuit is needed to calculate sample distances, which reduces the demand for quantum resources. Considering the QAML model is fragile to adversarial attacks, an adversarial sample generation strategy is designed based on the quantum gradient ascent method, effectively improving the robustness against the functional adversarial attack. Simulation results show that the QAML model can effectively distinguish samples of MNIST and Iris datasets and has higher <i>ϵ</i>-robustness accuracy over the general quantum metric learning. The QAML model is a fundamental research problem of machine learning. As a subroutine of classification and clustering tasks, the QAML model opens an avenue for exploring quantum advantages in machine learning.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00182-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5051299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-26DOI: 10.1140/epjqt/s40507-023-00178-x
Polina Acheva, Konstantin Zaitsev, Vladimir Zavodilenko, Anton Losev, Anqi Huang, Vadim Makarov
Attacks that control single-photon detectors in quantum key distribution using tailored bright illumination are capable of eavesdropping the secret key. Here we report an automated testbench that checks the detector’s vulnerabilities against these attacks. We illustrate its performance by testing a free-running detector that includes a rudimentary countermeasure measuring an average photocurrent. While our testbench automatically finds the detector to be controllable in a continuous-blinding regime, the countermeasure registers photocurrent significantly exceeding that in a quantum regime, thus revealing the attack. We then perform manually a pulsed blinding attack, which controls the detector intermittently. This attack is missed by the countermeasure in a wide range of blinding pulse durations and powers, still allowing to eavesdrop the key. We make recommendations for improvement of both the testbench and countermeasure.
{"title":"Automated verification of countermeasure against detector-control attack in quantum key distribution","authors":"Polina Acheva, Konstantin Zaitsev, Vladimir Zavodilenko, Anton Losev, Anqi Huang, Vadim Makarov","doi":"10.1140/epjqt/s40507-023-00178-x","DOIUrl":"10.1140/epjqt/s40507-023-00178-x","url":null,"abstract":"<div><p>Attacks that control single-photon detectors in quantum key distribution using tailored bright illumination are capable of eavesdropping the secret key. Here we report an automated testbench that checks the detector’s vulnerabilities against these attacks. We illustrate its performance by testing a free-running detector that includes a rudimentary countermeasure measuring an average photocurrent. While our testbench automatically finds the detector to be controllable in a continuous-blinding regime, the countermeasure registers photocurrent significantly exceeding that in a quantum regime, thus revealing the attack. We then perform manually a pulsed blinding attack, which controls the detector intermittently. This attack is missed by the countermeasure in a wide range of blinding pulse durations and powers, still allowing to eavesdrop the key. We make recommendations for improvement of both the testbench and countermeasure.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00178-x","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5416119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-26DOI: 10.1140/epjqt/s40507-023-00179-w
Kai Yang, Ruiqi Mao, Li He, Jiawei Yao, Jianbing Li, Zhanshan Sun, Yunqi Fu
Rydberg atom-based sensors using the atomic heterodyne technique demonstrate prominent performance on sensing sensitivity and thus have significant potential for radar, electronic reconnaissance, and communication applications. Here, we propose a local oscillator (LO) embedded field enhancement resonator to improve the sensitivity and integration of Rydberg atomic heterodyne sensors. In this approach, a vapor cell filled with cesium atoms is placed into the resonance structure for electric (E) field measurements. By integrating parallel-plate waveguide (PPWG) antennas and the resonator, the LO signal can be directly guided to the resonator using coaxial cable instead of the use of external antennas radiating through free space, allowing for a more flexible and practical Rydberg atom-based heterodyne technique. Based on the off-resonant Rydberg atomic heterodyne approach, for a radio frequency (RF) signal at 638 MHz, it is found that the sensitivity is 43 μV/cm(sqrt{text{Hz}}) in the absence of the resonator, while in the presence of our resonator, the sensitivity is down to 854.36 nV/cm(sqrt{text{Hz}}), indicating 50 times or 34 dB improvement capacity of the proposed resonator. This type of enhancement resonator is expected to benefit Rydberg atomic heterodyne applications in practical environments.
{"title":"Local oscillator port embedded field enhancement resonator for Rydberg atomic heterodyne technique","authors":"Kai Yang, Ruiqi Mao, Li He, Jiawei Yao, Jianbing Li, Zhanshan Sun, Yunqi Fu","doi":"10.1140/epjqt/s40507-023-00179-w","DOIUrl":"10.1140/epjqt/s40507-023-00179-w","url":null,"abstract":"<div><p>Rydberg atom-based sensors using the atomic heterodyne technique demonstrate prominent performance on sensing sensitivity and thus have significant potential for radar, electronic reconnaissance, and communication applications. Here, we propose a local oscillator (LO) embedded field enhancement resonator to improve the sensitivity and integration of Rydberg atomic heterodyne sensors. In this approach, a vapor cell filled with cesium atoms is placed into the resonance structure for electric (E) field measurements. By integrating parallel-plate waveguide (PPWG) antennas and the resonator, the LO signal can be directly guided to the resonator using coaxial cable instead of the use of external antennas radiating through free space, allowing for a more flexible and practical Rydberg atom-based heterodyne technique. Based on the off-resonant Rydberg atomic heterodyne approach, for a radio frequency (RF) signal at 638 MHz, it is found that the sensitivity is 43 <i>μ</i>V/cm<span>(sqrt{text{Hz}})</span> in the absence of the resonator, while in the presence of our resonator, the sensitivity is down to 854.36 nV/cm<span>(sqrt{text{Hz}})</span>, indicating 50 times or 34 dB improvement capacity of the proposed resonator. This type of enhancement resonator is expected to benefit Rydberg atomic heterodyne applications in practical environments.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00179-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5007985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-20DOI: 10.1140/epjqt/s40507-023-00180-3
Chong-Qiang Ye, Jian Li, Xiu-Bo Chen, Yanyan Hou, Zhuo Wang
Semi-quantum protocols serve as a bridge between quantum users and “classical” users with limited quantum capabilities, providing support for application scenarios that cannot afford the excessively high cost of quantum resources. In this paper, we present a semi-quantum key distribution (SQKD) protocol based on Bell states and single particles, which is designed for key distribution between different types of users. The protocol enables simultaneous key distribution between quantum and classical users, as well as key establishment between two classical users. The security analysis demonstrates that the protocol can reach the same level of security as the full quantum protocol. Furthermore, we extrapolate the proposed protocol to other semi-quantum protocols, such as semi-quantum key agreement and semi-quantum private comparison protocols. Compared with previous similar ones, our SQKD protocol and its extended versions can fulfill the requirements of their respective counterparts individually. Therefore, our SQKD protocol has the potential for broader applications in practical scenarios.
{"title":"Security and application of semi-quantum key distribution protocol for users with different quantum capabilities","authors":"Chong-Qiang Ye, Jian Li, Xiu-Bo Chen, Yanyan Hou, Zhuo Wang","doi":"10.1140/epjqt/s40507-023-00180-3","DOIUrl":"10.1140/epjqt/s40507-023-00180-3","url":null,"abstract":"<div><p>Semi-quantum protocols serve as a bridge between quantum users and “classical” users with limited quantum capabilities, providing support for application scenarios that cannot afford the excessively high cost of quantum resources. In this paper, we present a semi-quantum key distribution (SQKD) protocol based on Bell states and single particles, which is designed for key distribution between different types of users. The protocol enables simultaneous key distribution between quantum and classical users, as well as key establishment between two classical users. The security analysis demonstrates that the protocol can reach the same level of security as the full quantum protocol. Furthermore, we extrapolate the proposed protocol to other semi-quantum protocols, such as semi-quantum key agreement and semi-quantum private comparison protocols. Compared with previous similar ones, our SQKD protocol and its extended versions can fulfill the requirements of their respective counterparts individually. Therefore, our SQKD protocol has the potential for broader applications in practical scenarios.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00180-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4794555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-14DOI: 10.1140/epjqt/s40507-023-00176-z
Daniel Pereira, Margarida Almeida, Armando N. Pinto, Nuno A. Silva
Continuous-variable quantum key distribution (CV-QKD) provides a theoretical unconditionally secure solution to distribute symmetric keys among users in a communication network. However, the practical devices used to implement these systems are intrinsically imperfect, and, as a result, open the door to eavesdropper attacks. In this work, we study the impact of transmitter stage imperfections on the performance and security of a Discrete Modulated (DM) CV-QKD system using M-symbol Quadrature Amplitude Modulation (M-QAM) and Amplitude and Phase Shift Keying (M-APSK) coupled with Probabilistic Constellation Shaping (PCS). Assuming two different modulation stage topologies, we first deform the constellations and then evaluate the secure key rate achievable with the deformed constellation. The presented results show that, due to the erroneously estimated channel parameters, non-monitored imbalances greatly reduce the system’s performance, with situations where Bob and Alice estimate that no secure bits can be obtained while the real value of the key rate is still positive. Our results show the importance of monitoring these constellation imbalances and show that the optimal constellation may vary depending on the degree of device imperfection.
{"title":"Impact of transmitter imbalances on the security of continuous variables quantum key distribution","authors":"Daniel Pereira, Margarida Almeida, Armando N. Pinto, Nuno A. Silva","doi":"10.1140/epjqt/s40507-023-00176-z","DOIUrl":"10.1140/epjqt/s40507-023-00176-z","url":null,"abstract":"<div><p>Continuous-variable quantum key distribution (CV-QKD) provides a theoretical unconditionally secure solution to distribute symmetric keys among users in a communication network. However, the practical devices used to implement these systems are intrinsically imperfect, and, as a result, open the door to eavesdropper attacks. In this work, we study the impact of transmitter stage imperfections on the performance and security of a Discrete Modulated (DM) CV-QKD system using M-symbol Quadrature Amplitude Modulation (M-QAM) and Amplitude and Phase Shift Keying (M-APSK) coupled with Probabilistic Constellation Shaping (PCS). Assuming two different modulation stage topologies, we first deform the constellations and then evaluate the secure key rate achievable with the deformed constellation. The presented results show that, due to the erroneously estimated channel parameters, non-monitored imbalances greatly reduce the system’s performance, with situations where Bob and Alice estimate that no secure bits can be obtained while the real value of the key rate is still positive. Our results show the importance of monitoring these constellation imbalances and show that the optimal constellation may vary depending on the degree of device imperfection.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00176-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4576121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-08DOI: 10.1140/epjqt/s40507-023-00177-y
Tian-Ang Zheng, Ye Zheng, Lei Wang, Chang-Geng Liao
A theoretical scheme is proposed to generate significant amount of photon-phonon entanglement and asymmetric steering in a cavity magnomechanical system, which is constituted by trapping a yttrium iron garnet sphere in a microwave cavity. By applying a blue-detuned microwave driving field, we obtain an effective Hamiltonian where the magnon mode acting as an engineered resevoir cools the Bogoliubov modes of microwave cavity mode and mechanical mode via a beam-splitter-like interaction. By this means, the microwave cavity mode and mechanical mode can be driven to a two-mode squeezed state in the stationary limit. Particularly, strong two-way and one-way photon-phonon asymmetric quantum steering can be obtained with even equal dissipation. It is widely divergent with the conventional proposal, where additional unbalanced losses or noises should be imposed on the two subsystems. Our finding may be significant to expand our understanding of the essential physics of asymmetric steering and extend the potential application of the cavity spintronics to device-independent quantum key distribution.
{"title":"Dissipative generation of significant amount of photon-phonon asymmetric steering in magnomechanical interfaces","authors":"Tian-Ang Zheng, Ye Zheng, Lei Wang, Chang-Geng Liao","doi":"10.1140/epjqt/s40507-023-00177-y","DOIUrl":"10.1140/epjqt/s40507-023-00177-y","url":null,"abstract":"<div><p>A theoretical scheme is proposed to generate significant amount of photon-phonon entanglement and asymmetric steering in a cavity magnomechanical system, which is constituted by trapping a yttrium iron garnet sphere in a microwave cavity. By applying a blue-detuned microwave driving field, we obtain an effective Hamiltonian where the magnon mode acting as an engineered resevoir cools the Bogoliubov modes of microwave cavity mode and mechanical mode via a beam-splitter-like interaction. By this means, the microwave cavity mode and mechanical mode can be driven to a two-mode squeezed state in the stationary limit. Particularly, strong two-way and one-way photon-phonon asymmetric quantum steering can be obtained with even equal dissipation. It is widely divergent with the conventional proposal, where additional unbalanced losses or noises should be imposed on the two subsystems. Our finding may be significant to expand our understanding of the essential physics of asymmetric steering and extend the potential application of the cavity spintronics to device-independent quantum key distribution.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00177-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4349125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Semi-quantum key distribution describes a system in which a fully quantum user and classical user perform key distribution. The main advantage of key distribution is its security. Owing to the bottlenecks of existing technology, highly attenuated lasers and threshold detectors are required for semi-quantum key distribution; however, these components make semi-quantum key distribution susceptible to eavesdroppers. Our previous study presented the first semi-quantum key distribution experiment and verified the feasibility of the mirror protocol in 2021. Herein, we first build a semi-quantum key distribution channel model and use Gottesman-Lo-Lütkenhaus-Preskill theory to evaluate its safety performance in the case of a quasi-single photon source. Moreover, we determine that an eavesdropper can steal all information through the photon-number-splitting attack without being detected. Therefore, we add decoy states to the semi-quantum key distribution to estimate the furthest transmission distance and secure bit rate under asymptotic conditions. Semi-quantum key distribution can still be achieved safely with highly attenuated lasers and threshold detectors in 150 km.
半量子密钥分配描述了一种由全量子用户和经典用户进行密钥分配的系统。密钥分发的主要优点是它的安全性。由于现有技术的瓶颈,半量子密钥分发需要高衰减激光器和阈值探测器;然而,这些组件使得半量子密钥分发容易受到窃听者的攻击。我们之前的研究提出了第一个半量子密钥分发实验,并在2021年验证了镜像协议的可行性。本文首先建立了半量子密钥分配通道模型,并利用gottesman - lo - l tkenhaus- preskill理论对其在准单光子源情况下的安全性能进行了评价。此外,我们确定窃听者可以通过光子数分裂攻击窃取所有信息而不被发现。因此,我们在半量子密钥分配中加入诱饵态,以估计渐近条件下的最远传输距离和安全比特率。使用高度衰减的激光和阈值探测器,在150公里内仍然可以安全地实现半量子密钥分配。
{"title":"Decoy state semi-quantum key distribution","authors":"Shuang Dong, Shang Mi, Qingcheng Hou, Yutao Huang, Jindong Wang, Yafei Yu, Zhengjun Wei, Zhiming Zhang, Junbin Fang","doi":"10.1140/epjqt/s40507-023-00175-0","DOIUrl":"10.1140/epjqt/s40507-023-00175-0","url":null,"abstract":"<div><p>Semi-quantum key distribution describes a system in which a fully quantum user and classical user perform key distribution. The main advantage of key distribution is its security. Owing to the bottlenecks of existing technology, highly attenuated lasers and threshold detectors are required for semi-quantum key distribution; however, these components make semi-quantum key distribution susceptible to eavesdroppers. Our previous study presented the first semi-quantum key distribution experiment and verified the feasibility of the mirror protocol in 2021. Herein, we first build a semi-quantum key distribution channel model and use Gottesman-Lo-Lütkenhaus-Preskill theory to evaluate its safety performance in the case of a quasi-single photon source. Moreover, we determine that an eavesdropper can steal all information through the photon-number-splitting attack without being detected. Therefore, we add decoy states to the semi-quantum key distribution to estimate the furthest transmission distance and secure bit rate under asymptotic conditions. Semi-quantum key distribution can still be achieved safely with highly attenuated lasers and threshold detectors in 150 km.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00175-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5189761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}