{"title":"Dissipative Variational Quantum Algorithms for Gibbs State Preparation","authors":"Yigal Ilin;Itai Arad","doi":"10.1109/TQE.2024.3511419","DOIUrl":"https://doi.org/10.1109/TQE.2024.3511419","url":null,"abstract":"In recent years, variational quantum algorithms have gained significant attention due to their adaptability and efficiency on near-term quantum hardware. They have shown potential in a variety of tasks, including linear algebra, search problems, Gibbs, and ground state preparation. Nevertheless, the presence of noise in current day quantum hardware severely limits their performance. In this work, we introduce dissipative variational quantum algorithms (D-VQAs) by incorporating dissipative operations, such as qubit RESET and stochastic gates, as an intrinsic part of a variational quantum circuit. We argue that such dissipative variational algorithms possess some natural resilience to dissipative noise. We demonstrate how such algorithms can prepare Gibbs states over a wide range of quantum many-body Hamiltonians and temperatures, while significantly reducing errors due to both coherent and noncoherent noise. An additional advantage of our approach is that no ancilla qubits are need. Our results highlight the potential of D-VQAs to enhance the robustness and accuracy of variational quantum computations on noisy intermediate-scale quantum (NISQ) devices.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"6 ","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10777530","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"TAQNet: Traffic-Aware Minimum-Cost Quantum Communication Network Planning","authors":"Ilora Maity;Junaid ur Rehman;Symeon Chatzinotas","doi":"10.1109/TQE.2024.3509019","DOIUrl":"https://doi.org/10.1109/TQE.2024.3509019","url":null,"abstract":"Quantum key distribution (QKD) provides a secure method to exchange encrypted information between two parties in a quantum communication infrastructure (QCI). The primary challenge in deploying a QCI is the cost of using optical fibers and trusted repeater nodes (TRNs). Practical systems combine quantum and classical channels on the same fiber to reduce the cost of fibers dedicated to QKD. In such a system with quantum-classical coexistence, the optimal distribution of QKD requests with minimal deployment cost and power usage on the multiplexed links is challenging due to the diverse key rate demands of the requests, number of classical and quantum channels, guard band spacing between classical and quantum channels, and secret key rate of the quantum channels that decreases with distance. To address these challenges, in this work, we propose a Steiner tree-based approach for constructing a QCI that connects all quantum nodes with minimum TRNs. In addition, we propose a genetic algorithm-based solution to optimally distribute the end-to-end QKD requests over the QCI. We also determine feasible optical bypass routes to reduce the overall energy consumption in the network further. The proposed approach reduces the QCI deployment cost by 19.42% compared to the benchmark MST-Baseline. Also, on average, TAQNet with optical bypass achieves 4.69 kbit per Joule more energy efficiency compared to the nonbypass approach.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"6 ","pages":"1-16"},"PeriodicalIF":0.0,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10771724","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142859137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"FPGA-Based Synchronization of Frequency-Domain Interferometer for QKD","authors":"Nishanth Chandra;Pradeep Kumar Krishnamurthy","doi":"10.1109/TQE.2024.3507155","DOIUrl":"https://doi.org/10.1109/TQE.2024.3507155","url":null,"abstract":"In this article, we propose and experimentally demonstrate a novel synchronization method for quantum key distribution (QKD) systems. The method consists of maximizing the visibility of frequency-domain interference of optical sidebands about an optical carrier at the receiver node. The sidebands are generated by phase modulation of the optical carrier by an radio-frequency (RF) signal whose phase can be dynamically varied. The phase-variable RF signal is generated by the field-programmable gate array (FPGA) at the transmitter and the receiver using GTX transceivers. In order to facilitate this, we use square waveforms for RF signal instead of the conventional sinusoidal signals. We derive mathematical expressions for sideband power as a function of the phase difference between RF signals at transmitter and receiver. The phase is adjusted using dynamic phase shifter module, implemented by the FPGA. We propose a complete workflow that allows transmitter and receiver synchronization to within 12.6 ps directly over the quantum channel of QKD systems. Once synchronized, the same system can be switched over to quantum transmission by user-defined time delay. The workflow was implemented on a Xilinx Kintex-7 KC705 FPGA board. We studied the robustness of our technique by evaluating the stability of the interferometer over an operation of 10 min with standard deviation of interference to be less than 9% of the mean detection amplitude.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"6 ","pages":"1-10"},"PeriodicalIF":0.0,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10769019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Grover's Oracle for the Shortest Vector Problem and Its Application in Hybrid Classical–Quantum Solvers","authors":"Miloš Prokop;Petros Wallden;David Joseph","doi":"10.1109/TQE.2024.3501683","DOIUrl":"https://doi.org/10.1109/TQE.2024.3501683","url":null,"abstract":"Finding the shortest vector in a lattice is a problem that is believed to be hard both for classical and quantum computers. Many major postquantum secure cryptosystems base their security on the hardness of the shortest vector problem (SVP) (Moody, 2023). Finding the best classical, quantum, or hybrid classical–quantum algorithms for the SVP is necessary to select cryptosystem parameters that offer a sufficient level of security. Grover's search quantum algorithm provides a generic quadratic speedup, given access to an oracle implementing some function, which describes when a solution is found. In this article, we provide concrete implementation of such an oracle for the SVP. We define the circuit and evaluate costs in terms of the number of qubits, the number of gates, depth, and T-quantum cost. We then analyze how to combine Grover's quantum search for small SVP instances with state-of-the-art classical solvers that use well-known algorithms, such as the block Korkine Zolotorev (Schnorr and Euchner, 1994), where the former is used as a subroutine. This could enable solving larger instances of SVP with higher probability than classical state-of-the-art records, but still very far from posing any threat to cryptosystems being considered for standardization. Depending on the technology available, there is a spectrum of tradeoffs in creating this combination.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"6 ","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10756628","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jorge M. Ramirez;Elaine Wong;Caio Alves;Sarah Chehade;Ryan Bennink
{"title":"Expressiveness of Commutative Quantum Circuits: A Probabilistic Approach","authors":"Jorge M. Ramirez;Elaine Wong;Caio Alves;Sarah Chehade;Ryan Bennink","doi":"10.1109/TQE.2024.3488518","DOIUrl":"https://doi.org/10.1109/TQE.2024.3488518","url":null,"abstract":"This study investigates the frame potential and expressiveness of commutative quantum circuits. Based on the Fourier series representation of these circuits, we express quantum expectation and pairwise fidelity as characteristic functions of random variables, and we characterize expressiveness as the recurrence probability of a random walk on a lattice. A central outcome of our work includes formulas to approximate the frame potential and expressiveness for any commutative quantum circuit, underpinned by convergence theorems in the probability theory. We identify the lattice volume of the random walk as means to approximate expressiveness based on circuit architecture. In the specific case of commutative circuits involving Pauli-\u0000<inline-formula><tex-math>$Z$</tex-math></inline-formula>\u0000 rotations, we provide theoretical results relating expressiveness and circuit structure. Our probabilistic representation also provides means for bounding and approximately calculating the frame potential of a circuit through sampling methods.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"5 ","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10738429","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142736338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin Gys;Lander Burgelman;Kristiaan De Greve;Georges Gielen;Francky Catthoor
{"title":"Hybrid Hamiltonian Simulation Approach for the Analysis of Quantum Error Correction Protocol Robustness","authors":"Benjamin Gys;Lander Burgelman;Kristiaan De Greve;Georges Gielen;Francky Catthoor","doi":"10.1109/TQE.2024.3486546","DOIUrl":"https://doi.org/10.1109/TQE.2024.3486546","url":null,"abstract":"The development of future full-scale quantum computers (QCs) not only comprises the design of good quality qubits, but also entails the design of classical complementary metal–oxide semiconductor (CMOS) control circuitry and optimized operation protocols. The construction and implementation of quantum error correction (QEC) protocols, necessary for correcting the errors that inevitably occur in the physical qubit layer, form a crucial step in this design process. The steadily rising numbers of qubits in a single system make the development of small-scale quantum architectures that are able to execute such protocols a pressing challenge. Similar to classical systems, optimized simulation tools can greatly improve the efficiency of the design process. We propose an automated simulation framework for the development of qubit microarchitectures, in which the effects of design choices in the physical qubit layer on the performance of QEC protocols can be evaluated, whereas the focus in the current state-of-the-art design tools only lies on the simulation of the individual quantum gates. The hybrid Hamiltonian framework introduces the innovative combination of a hybrid nature that allows to incorporate several levels throughout the QC stack, with optimized embedded solvers. This provides the level of detail required for an in-depth analysis of the QEC protocol's stability.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"5 ","pages":"1-11"},"PeriodicalIF":0.0,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10735416","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142691744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fixed-Point Grover Adaptive Search for Quadratic Binary Optimization Problems","authors":"Ákos Nagy;Jaime Park;Cindy Zhang;Atithi Acharya;Alex Khan","doi":"10.1109/TQE.2024.3484650","DOIUrl":"https://doi.org/10.1109/TQE.2024.3484650","url":null,"abstract":"In this article, we study a Grover-type method for quadratic unconstrained binary optimization (QUBO) problems. For an \u0000<inline-formula><tex-math>$n$</tex-math></inline-formula>\u0000-dimensional QUBO problem with \u0000<inline-formula><tex-math>$m$</tex-math></inline-formula>\u0000 nonzero terms, we construct a marker oracle for such problems with a tunable parameter, \u0000<inline-formula><tex-math>$Lambda in [ 1, m ] cap mathbb {Z}$</tex-math></inline-formula>\u0000. At \u0000<inline-formula><tex-math>$d in mathbb {Z}_+$</tex-math></inline-formula>\u0000 precision, the oracle uses \u0000<inline-formula><tex-math>$O (n + Lambda d)$</tex-math></inline-formula>\u0000 qubits and has total depth of \u0000<inline-formula><tex-math>$O (frac{m}{Lambda } log _{2} (n) + log _{2} (d))$</tex-math></inline-formula>\u0000 and a non-Clifford depth of \u0000<inline-formula><tex-math>$O (frac{m}{Lambda })$</tex-math></inline-formula>\u0000. Moreover, each qubit is required to be connected to at most \u0000<inline-formula><tex-math>$O (log _{2} (Lambda + d))$</tex-math></inline-formula>\u0000 other qubits. In the case of a maximum graph cuts, as \u0000<inline-formula><tex-math>$d = 2 leftlceil log _{2} (n) rightrceil$</tex-math></inline-formula>\u0000 always suffices, the depth of the marker oracle can be made as shallow as \u0000<inline-formula><tex-math>$O (log _{2} (n))$</tex-math></inline-formula>\u0000. For all values of \u0000<inline-formula><tex-math>$Lambda$</tex-math></inline-formula>\u0000, the non-Clifford gate count of these oracles is strictly lower (at least by a factor of \u0000<inline-formula><tex-math>$sim 2$</tex-math></inline-formula>\u0000) than previous constructions. Furthermore, we introduce a novel fixed-point Grover adaptive search for QUBO problems, using our oracle design and a hybrid fixed-point Grover search, motivated by the works of Boyer et al. (1988) and Li et al. (2019). This method has better performance guarantees than previous Grover adaptive search methods. Some of our results are novel and useful for any method based on the fixed-point Grover search. Finally, we give a heuristic argument that, with high probability and in \u0000<inline-formula><tex-math>$O (frac{log _{2} (n)}{sqrt{epsilon }})$</tex-math></inline-formula>\u0000 time, this adaptive method finds a configuration that is among the best \u0000<inline-formula><tex-math>$epsilon 2^{n}$</tex-math></inline-formula>\u0000 ones.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"5 ","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10726869","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohadeseh Azari;Paul Polakos;Kaushik P. Seshadreesan
{"title":"Quantum Switches for Gottesman–Kitaev–Preskill Qubit-Based All-Photonic Quantum Networks","authors":"Mohadeseh Azari;Paul Polakos;Kaushik P. Seshadreesan","doi":"10.1109/TQE.2024.3476009","DOIUrl":"https://doi.org/10.1109/TQE.2024.3476009","url":null,"abstract":"The Gottesman–Kitaev–Preskill (GKP) code, being information theoretically near optimal for quantum communication over Gaussian thermal-loss optical channels, is likely to be the encoding of choice for advanced quantum networks of the future. Quantum repeaters based on GKP-encoded light have been shown to support high end-to-end entanglement rates across large distances despite realistic finite squeezing in GKP code preparation and homodyne detection inefficiencies. Here, we introduce a quantum switch for GKP qubit-based quantum networks. Its architecture involves multiplexed GKP qubit-based entanglement link generation with clients and their all-photonic storage, enabled by GKP qubit graph state resources. The switch uses a multiclient generalization of a recently introduced entanglement-ranking-based link matching heuristic for bipartite entanglement distribution between clients via entanglement swapping. Since generating the GKP qubit graph state resource is hardware intensive, given a total resource budget and an arbitrary layout of clients, we address the question of their optimal allocation to the different client–pair connections served by the switch such that the switch's sum throughput is maximized while also being fair in terms of the individual entanglement rates. We illustrate our results for an exemplary data center network, where the data center is a client of a switch, and all of its other clients aim to connect to the data center alone—a scenario that also captures the general case of a gateway router connecting a local area network to a global network. Together with compatible quantum repeaters, our quantum switch provides a way to realize quantum networks of arbitrary topology.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"5 ","pages":"1-15"},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10720623","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"HyQ2: A Hybrid Quantum Neural Network for NextG Vulnerability Detection","authors":"Yifeng Peng;Xinyi Li;Zhiding Liang;Ying Wang","doi":"10.1109/TQE.2024.3481280","DOIUrl":"https://doi.org/10.1109/TQE.2024.3481280","url":null,"abstract":"As fifth-generation (5G) and next-generation communication systems advance and find widespread application in critical infrastructures, the importance of vulnerability detection becomes increasingly critical. The growing complexity of these systems necessitates rigorous testing and analysis, with stringent requirements for both accuracy and speed. In this article, we present a state-of-the-art supervised hybrid quantum neural network named HyQ2 for vulnerability detection in next-generation wireless communication systems. The proposed HyQ2 is integrated with graph-embedded and quantum variational circuits to validate and detect vulnerabilities from the 5G system's state transitions based on graphs extracted from log files. We address the limitations of classical machine learning models in processing the intrinsic linkage relationships of high-dimensional data. These models often suffer from dead neurons and excessively large outputs caused by the unbounded range of the rectified linear unit (ReLU) activation function. We propose the HyQ2 method to overcome these challenges, which constructs quantum neurons by selecting random neurons' outputs from a classical neural network. These quantum neurons are then utilized to capture more complex relationships, effectively limiting the ReLU output. Using only two qubits, our validation results demonstrate that HyQ2 outperforms traditional classical machine learning models in vulnerability detection. The small and compact variational circuit of HyQ2 minimizes the noise and errors in the measurement. Our results demonstrate that HyQ2 achieves a high area under the curve (AUC) value of 0.9708 and an accuracy of 95.91%. To test the model's performance in quantum noise environments, we simulate quantum noise by adding bit flipping, phase flipping, amplitude damping, and depolarizing noise. The results show that the prediction accuracy and receiver operating characteristic AUC value fluctuate around 0.2%, indicating HyQ2’s robustness in noisy quantum environments. In addition, the noise resilience and robustness of the HyQ2 algorithm were substantiated through experiments on the IBM quantum machine with only a 0.2% decrease compared to the simulation results.","PeriodicalId":100644,"journal":{"name":"IEEE Transactions on Quantum Engineering","volume":"5 ","pages":"1-19"},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10716796","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}