Yilun Xu, Gang-Ming Huang, J. Balewski, A. Morvan, Kasra Nowrouzi, D. Santiago, R. Naik, B. Mitchell, I. Siddiqi
As the size and complexity of a quantum computer increases, quantum bit (qubit) characterization and gate optimization become complex and time-consuming tasks. Current calibration techniques require complicated and verbose measurements to tune up qubits and gates, which cannot easily expand to the large-scale quantum systems. We develop a concise and automatic calibration protocol to characterize qubits and optimize gates using QubiC, which is an open source FPGA (field-programmable gate array)-based control and measurement system for superconducting quantum information processors. We propose multi-dimensional loss-based optimization of single-qubit gates and full XY-plane measurement method for the two-qubit CNOT gate calibration. We demonstrate the QubiC automatic calibration protocols are capable of delivering high-fidelity gates on the state-of-the-art transmon-type processor operating at the Advanced Quantum Testbed at Lawrence Berkeley National Laboratory. The single-qubit and two-qubit Clifford gate infidelities measured by randomized benchmarking are of 4.9(1.1) × 10-4 and 1.4(3) × 10-2, respectively.
{"title":"Automatic Qubit Characterization and Gate Optimization with QubiC","authors":"Yilun Xu, Gang-Ming Huang, J. Balewski, A. Morvan, Kasra Nowrouzi, D. Santiago, R. Naik, B. Mitchell, I. Siddiqi","doi":"10.1145/3529397","DOIUrl":"https://doi.org/10.1145/3529397","url":null,"abstract":"As the size and complexity of a quantum computer increases, quantum bit (qubit) characterization and gate optimization become complex and time-consuming tasks. Current calibration techniques require complicated and verbose measurements to tune up qubits and gates, which cannot easily expand to the large-scale quantum systems. We develop a concise and automatic calibration protocol to characterize qubits and optimize gates using QubiC, which is an open source FPGA (field-programmable gate array)-based control and measurement system for superconducting quantum information processors. We propose multi-dimensional loss-based optimization of single-qubit gates and full XY-plane measurement method for the two-qubit CNOT gate calibration. We demonstrate the QubiC automatic calibration protocols are capable of delivering high-fidelity gates on the state-of-the-art transmon-type processor operating at the Advanced Quantum Testbed at Lawrence Berkeley National Laboratory. The single-qubit and two-qubit Clifford gate infidelities measured by randomized benchmarking are of 4.9(1.1) × 10-4 and 1.4(3) × 10-2, respectively.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115866572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thien Nguyen, Dmitry I. Lyakh, E. Dumitrescu, David Clark, Jeffery Larkin, A. McCaskey
The numerical simulation of quantum circuits is an indispensable tool for development, verification, and validation of hybrid quantum-classical algorithms intended for near-term quantum co-processors. The emergence of exascale high-performance computing (HPC) platforms presents new opportunities for pushing the boundaries of quantum circuit simulation. We present a modernized version of the Tensor Network Quantum Virtual Machine (TNQVM) that serves as the quantum circuit simulation backend in the eXtreme-scale ACCelerator (XACC) framework. The new version is based on the scalable tensor network processing library ExaTN (Exascale Tensor Networks). It provides multiple configurable quantum circuit simulators that perform either an exact quantum circuit simulation via the full tensor network contraction or an approximate simulation via a suitably chosen tensor factorization scheme. Upon necessity, stochastic noise modeling from real quantum processors is incorporated into the simulations by modeling quantum channels with Kraus tensors. By combining the portable XACC quantum programming frontend and the scalable ExaTN numerical processing backend, we introduce an end-to-end virtual quantum development environment that can scale from laptops to future exascale platforms. We report initial benchmarks of our framework, which include a demonstration of the distributed execution, incorporation of quantum decoherence models, and simulation of the random quantum circuits used for the certification of quantum supremacy on Google’s Sycamore superconducting architecture.
{"title":"Tensor Network Quantum Virtual Machine for Simulating Quantum Circuits at Exascale","authors":"Thien Nguyen, Dmitry I. Lyakh, E. Dumitrescu, David Clark, Jeffery Larkin, A. McCaskey","doi":"10.1145/3547334","DOIUrl":"https://doi.org/10.1145/3547334","url":null,"abstract":"The numerical simulation of quantum circuits is an indispensable tool for development, verification, and validation of hybrid quantum-classical algorithms intended for near-term quantum co-processors. The emergence of exascale high-performance computing (HPC) platforms presents new opportunities for pushing the boundaries of quantum circuit simulation. We present a modernized version of the Tensor Network Quantum Virtual Machine (TNQVM) that serves as the quantum circuit simulation backend in the eXtreme-scale ACCelerator (XACC) framework. The new version is based on the scalable tensor network processing library ExaTN (Exascale Tensor Networks). It provides multiple configurable quantum circuit simulators that perform either an exact quantum circuit simulation via the full tensor network contraction or an approximate simulation via a suitably chosen tensor factorization scheme. Upon necessity, stochastic noise modeling from real quantum processors is incorporated into the simulations by modeling quantum channels with Kraus tensors. By combining the portable XACC quantum programming frontend and the scalable ExaTN numerical processing backend, we introduce an end-to-end virtual quantum development environment that can scale from laptops to future exascale platforms. We report initial benchmarks of our framework, which include a demonstration of the distributed execution, incorporation of quantum decoherence models, and simulation of the random quantum circuits used for the certification of quantum supremacy on Google’s Sycamore superconducting architecture.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127693871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Myrto Arapinis, N. Lamprou, Elham Kashefi, Anna Pappa
Recent advances indicate that quantum computers will soon be reality. Motivated by this ever more realistic threat for existing classical cryptographic protocols, researchers have developed several schemes to resist “quantum attacks.” In particular, for electronic voting (e-voting), several schemes relying on properties of quantum mechanics have been proposed. However, each of these proposals comes with a different and often not well-articulated corruption model, has different objectives, and is accompanied by security claims that are never formalized and are at best justified only against specific attacks. To address this, we propose the first formal security definitions for quantum e-voting protocols. With these at hand, we systematize and evaluate the security of previously proposed quantum e-voting protocols; we examine the claims of these works concerning privacy, correctness, and verifiability, and if they are correctly attributed to the proposed protocols. In all non-trivial cases, we identify specific quantum attacks that violate these properties. We argue that the cause of these failures lies in the absence of formal security models and references to the existing cryptographic literature.
{"title":"Definitions and Security of Quantum Electronic Voting","authors":"Myrto Arapinis, N. Lamprou, Elham Kashefi, Anna Pappa","doi":"10.1145/3450144","DOIUrl":"https://doi.org/10.1145/3450144","url":null,"abstract":"Recent advances indicate that quantum computers will soon be reality. Motivated by this ever more realistic threat for existing classical cryptographic protocols, researchers have developed several schemes to resist “quantum attacks.” In particular, for electronic voting (e-voting), several schemes relying on properties of quantum mechanics have been proposed. However, each of these proposals comes with a different and often not well-articulated corruption model, has different objectives, and is accompanied by security claims that are never formalized and are at best justified only against specific attacks. To address this, we propose the first formal security definitions for quantum e-voting protocols. With these at hand, we systematize and evaluate the security of previously proposed quantum e-voting protocols; we examine the claims of these works concerning privacy, correctness, and verifiability, and if they are correctly attributed to the proposed protocols. In all non-trivial cases, we identify specific quantum attacks that violate these properties. We argue that the cause of these failures lies in the absence of formal security models and references to the existing cryptographic literature.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"63 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128527343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We establish an improved classical algorithm for solving linear systems in a model analogous to the QRAM that is used by quantum linear solvers. Precisely, for the linear system ( A{bf x}= {bf b} ) , we show that there is a classical algorithm that outputs a data structure for ( {bf x} ) allowing sampling and querying to the entries, where ( {bf x} ) is such that ( Vert {bf x}- A^{+}{bf b}Vert le epsilon Vert A^{+}{bf b}Vert ) . This output can be viewed as a classical analogue to the output of quantum linear solvers. The complexity of our algorithm is ( widetilde{O}(kappa _F^6 kappa ^2/epsilon ^2) ) , where ( kappa _F = Vert AVert _FVert A^{+}Vert ) and ( kappa = Vert AVert Vert A^{+}Vert ) . This improves the previous best algorithm [Gilyén, Song and Tang, arXiv:2009.07268] of complexity ( widetilde{O}(kappa _F^6 kappa ^6/epsilon ^4) ) . Our algorithm is based on the randomized Kaczmarz method, which is a particular case of stochastic gradient descent. We also find that when A is row sparse, this method already returns an approximate solution ( {bf x} ) in time ( widetilde{O}(kappa _F^2) ) , while the best quantum algorithm known returns ( | {bf x} rangle ) in time ( widetilde{O}(kappa _F) ) when A is stored in the QRAM data structure. As a result, assuming access to QRAM and if A is row sparse, the speedup based on current quantum algorithms is quadratic.
我们建立了一种改进的经典算法来求解线性系统的模型，类似于量子线性求解器所使用的QRAM。准确地说，对于线性系统( A{bf x}= {bf b} )，我们展示了一个经典算法，它为( {bf x} )输出一个数据结构，允许对条目进行采样和查询，其中( {bf x} )使得( Vert {bf x}- A^{+}{bf b}Vert le epsilon Vert A^{+}{bf b}Vert )。这种输出可以看作是量子线性解算器输出的经典模拟。我们算法的复杂度为( widetilde{O}(kappa _F^6 kappa ^2/epsilon ^2) )，其中( kappa _F = Vert AVert _FVert A^{+}Vert )和( kappa = Vert AVert Vert A^{+}Vert )。这提高了之前复杂度( widetilde{O}(kappa _F^6 kappa ^6/epsilon ^4) )的最佳算法[gily， Song and Tang, arXiv:2009.07268]。我们的算法基于随机Kaczmarz方法，这是随机梯度下降的一种特殊情况。我们还发现，当A是行稀疏时，该方法已经在( widetilde{O}(kappa _F^2) )时间内返回近似解( {bf x} )，而当A存储在QRAM数据结构中时，已知的最佳量子算法在( widetilde{O}(kappa _F) )时间内返回( | {bf x} rangle )。因此，假设访问QRAM并且如果a是行稀疏的，基于当前量子算法的加速是二次的。
{"title":"Faster Quantum-inspired Algorithms for Solving Linear Systems","authors":"Changpeng Shao, A. Montanaro","doi":"10.1145/3520141","DOIUrl":"https://doi.org/10.1145/3520141","url":null,"abstract":"We establish an improved classical algorithm for solving linear systems in a model analogous to the QRAM that is used by quantum linear solvers. Precisely, for the linear system ( A{bf x}= {bf b} ) , we show that there is a classical algorithm that outputs a data structure for ( {bf x} ) allowing sampling and querying to the entries, where ( {bf x} ) is such that ( Vert {bf x}- A^{+}{bf b}Vert le epsilon Vert A^{+}{bf b}Vert ) . This output can be viewed as a classical analogue to the output of quantum linear solvers. The complexity of our algorithm is ( widetilde{O}(kappa _F^6 kappa ^2/epsilon ^2) ) , where ( kappa _F = Vert AVert _FVert A^{+}Vert ) and ( kappa = Vert AVert Vert A^{+}Vert ) . This improves the previous best algorithm [Gilyén, Song and Tang, arXiv:2009.07268] of complexity ( widetilde{O}(kappa _F^6 kappa ^6/epsilon ^4) ) . Our algorithm is based on the randomized Kaczmarz method, which is a particular case of stochastic gradient descent. We also find that when A is row sparse, this method already returns an approximate solution ( {bf x} ) in time ( widetilde{O}(kappa _F^2) ) , while the best quantum algorithm known returns ( | {bf x} rangle ) in time ( widetilde{O}(kappa _F) ) when A is stored in the QRAM data structure. As a result, assuming access to QRAM and if A is row sparse, the speedup based on current quantum algorithms is quadratic.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130291003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Non-linearity of a Boolean function indicates how far it is from any linear function. Despite there being several strong results about identifying a linear function and distinguishing one from a sufficiently non-linear function, we found a surprising lack of work on computing the non-linearity of a function. The non-linearity is related to the Walsh coefficient with the largest absolute value; however, the naive attempt of picking the maximum after constructing a Walsh spectrum requires Θ (2n) queries to an n-bit function. We improve the scenario by designing highly efficient quantum and randomised algorithms to approximate the non-linearity allowing additive error, denoted λ, with query complexities that depend polynomially on λ. We prove lower bounds to show that these are not very far from the optimal ones. The number of queries made by our randomised algorithm is linear in n, already an exponential improvement, and the number of queries made by our quantum algorithm is surprisingly independent of n. Our randomised algorithm uses a Goldreich-Levin style of navigating all Walsh coefficients and our quantum algorithm uses a clever combination of Deutsch-Jozsa, amplitude amplification and amplitude estimation to improve upon the existing quantum versions of the Goldreich-Levin technique.
{"title":"Quantum and Randomised Algorithms for Non-linearity Estimation","authors":"Debajyoti Bera, Sapv Tharrmashastha","doi":"10.1145/3456509","DOIUrl":"https://doi.org/10.1145/3456509","url":null,"abstract":"Non-linearity of a Boolean function indicates how far it is from any linear function. Despite there being several strong results about identifying a linear function and distinguishing one from a sufficiently non-linear function, we found a surprising lack of work on computing the non-linearity of a function. The non-linearity is related to the Walsh coefficient with the largest absolute value; however, the naive attempt of picking the maximum after constructing a Walsh spectrum requires Θ (2n) queries to an n-bit function. We improve the scenario by designing highly efficient quantum and randomised algorithms to approximate the non-linearity allowing additive error, denoted λ, with query complexities that depend polynomially on λ. We prove lower bounds to show that these are not very far from the optimal ones. The number of queries made by our randomised algorithm is linear in n, already an exponential improvement, and the number of queries made by our quantum algorithm is surprisingly independent of n. Our randomised algorithm uses a Goldreich-Levin style of navigating all Walsh coefficients and our quantum algorithm uses a clever combination of Deutsch-Jozsa, amplitude amplification and amplitude estimation to improve upon the existing quantum versions of the Goldreich-Levin technique.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116946586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stuart M. Harwood, Dimitar Trenev, Spencer T. Stober, P. Barkoutsos, Tanvi P. Gujarati, S. Mostame, Donny Greenberg
The variational quantum eigensolver (VQE) is a hybrid quantum-classical algorithm for finding the minimum eigenvalue of a Hamiltonian that involves the optimization of a parameterized quantum circuit. Since the resulting optimization problem is in general nonconvex, the method can converge to suboptimal parameter values that do not yield the minimum eigenvalue. In this work, we address this shortcoming by adopting the concept of variational adiabatic quantum computing (VAQC) as a procedure to improve VQE. In VAQC, the ground state of a continuously parameterized Hamiltonian is approximated via a parameterized quantum circuit. We discuss some basic theory of VAQC to motivate the development of a hybrid quantum-classical homotopy continuation method. The proposed method has parallels with a predictor-corrector method for numerical integration of differential equations. While there are theoretical limitations to the procedure, we see in practice that VAQC can successfully find good initial circuit parameters to initialize VQE. We demonstrate this with two examples from quantum chemistry. Through these examples, we provide empirical evidence that VAQC, combined with other techniques (an adaptive termination criteria for the classical optimizer and a variance-based resampling method for the expectation evaluation), can provide more accurate solutions than “plain” VQE, for the same amount of effort.
{"title":"Improving the Variational Quantum Eigensolver Using Variational Adiabatic Quantum Computing","authors":"Stuart M. Harwood, Dimitar Trenev, Spencer T. Stober, P. Barkoutsos, Tanvi P. Gujarati, S. Mostame, Donny Greenberg","doi":"10.1145/3479197","DOIUrl":"https://doi.org/10.1145/3479197","url":null,"abstract":"The variational quantum eigensolver (VQE) is a hybrid quantum-classical algorithm for finding the minimum eigenvalue of a Hamiltonian that involves the optimization of a parameterized quantum circuit. Since the resulting optimization problem is in general nonconvex, the method can converge to suboptimal parameter values that do not yield the minimum eigenvalue. In this work, we address this shortcoming by adopting the concept of variational adiabatic quantum computing (VAQC) as a procedure to improve VQE. In VAQC, the ground state of a continuously parameterized Hamiltonian is approximated via a parameterized quantum circuit. We discuss some basic theory of VAQC to motivate the development of a hybrid quantum-classical homotopy continuation method. The proposed method has parallels with a predictor-corrector method for numerical integration of differential equations. While there are theoretical limitations to the procedure, we see in practice that VAQC can successfully find good initial circuit parameters to initialize VQE. We demonstrate this with two examples from quantum chemistry. Through these examples, we provide empirical evidence that VAQC, combined with other techniques (an adaptive termination criteria for the classical optimizer and a variance-based resampling method for the expectation evaluation), can provide more accurate solutions than “plain” VQE, for the same amount of effort.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122489593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Ittah, Thomas Häner, Vadym Kliuchnikov, T. Hoefler
We propose an IR for quantum computing that directly exposes quantum and classical data dependencies for the purpose of optimization. The Quantum Intermediate Representation for Optimization(QIRO) consists of two dialects, one input dialect and one that is specifically tailored to enable quantum-classical co-optimization. While the first employs a perhaps more intuitive memory-semantics (quantum operations act on qubits via side-effects), the latter uses value-semantics (operations consume and produce states) to integrate quantum dataflow in the IR’s Static Single Assignment (SSA) graph. Crucially, this allows for a host of optimizations that leverage dataflow analysis. We discuss how to map existing quantum programming languages to the input dialect and how to lower the resulting IR to the optimization dialect. We present a prototype implementation based on MLIR that includes several quantum-specific optimization passes. Our benchmarks show that significant improvements in resource requirements are possible even through static optimization. In contrast to circuit optimization at run time, this is achieved while incurring only a small constant overhead in compilation time, making this a compelling approach for quantum program optimization at application scale.
{"title":"QIRO: A Static Single Assignment-based Quantum Program Representation for Optimization","authors":"D. Ittah, Thomas Häner, Vadym Kliuchnikov, T. Hoefler","doi":"10.1145/3491247","DOIUrl":"https://doi.org/10.1145/3491247","url":null,"abstract":"We propose an IR for quantum computing that directly exposes quantum and classical data dependencies for the purpose of optimization. The Quantum Intermediate Representation for Optimization(QIRO) consists of two dialects, one input dialect and one that is specifically tailored to enable quantum-classical co-optimization. While the first employs a perhaps more intuitive memory-semantics (quantum operations act on qubits via side-effects), the latter uses value-semantics (operations consume and produce states) to integrate quantum dataflow in the IR’s Static Single Assignment (SSA) graph. Crucially, this allows for a host of optimizations that leverage dataflow analysis. We discuss how to map existing quantum programming languages to the input dialect and how to lower the resulting IR to the optimization dialect. We present a prototype implementation based on MLIR that includes several quantum-specific optimization passes. Our benchmarks show that significant improvements in resource requirements are possible even through static optimization. In contrast to circuit optimization at run time, this is achieved while incurring only a small constant overhead in compilation time, making this a compelling approach for quantum program optimization at application scale.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121161946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John K. Golden, Andreas Bärtschi, Daniel O’Malley, S. Eidenbenz
We study the status of fair sampling on Noisy Intermediate Scale Quantum (NISQ) devices, in particular the IBM Q family of backends. Using the recently introduced Grover Mixer-QAOA algorithm for discrete optimization, we generate fair sampling circuits to solve six problems of varying difficulty, each with several optimal solutions, which we then run on twenty backends across the IBM Q system. For a given circuit evaluated on a specific set of qubits, we evaluate: how frequently the qubits return an optimal solution to the problem, the fairness with which the qubits sample from all optimal solutions, and the reported hardware error rate of the qubits. To quantify fairness, we define a novel metric based on Pearson’s χ2 test. We find that fairness is relatively high for circuits with small and large error rates, but drops for circuits with medium error rates. This indicates that structured errors dominate in this regime, while unstructured errors, which are random and thus inherently fair, dominate in noisier qubits and longer circuits. Our results show that fairness can be a powerful tool for understanding the intricate web of errors affecting current NISQ hardware.
{"title":"Fair Sampling Error Analysis on NISQ Devices","authors":"John K. Golden, Andreas Bärtschi, Daniel O’Malley, S. Eidenbenz","doi":"10.1145/3510857","DOIUrl":"https://doi.org/10.1145/3510857","url":null,"abstract":"We study the status of fair sampling on Noisy Intermediate Scale Quantum (NISQ) devices, in particular the IBM Q family of backends. Using the recently introduced Grover Mixer-QAOA algorithm for discrete optimization, we generate fair sampling circuits to solve six problems of varying difficulty, each with several optimal solutions, which we then run on twenty backends across the IBM Q system. For a given circuit evaluated on a specific set of qubits, we evaluate: how frequently the qubits return an optimal solution to the problem, the fairness with which the qubits sample from all optimal solutions, and the reported hardware error rate of the qubits. To quantify fairness, we define a novel metric based on Pearson’s χ2 test. We find that fairness is relatively high for circuits with small and large error rates, but drops for circuits with medium error rates. This indicates that structured errors dominate in this regime, while unstructured errors, which are random and thus inherently fair, dominate in noisier qubits and longer circuits. Our results show that fairness can be a powerful tool for understanding the intricate web of errors affecting current NISQ hardware.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123207814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Welcome to the inaugural issue of ACM Transactions on Quantum Computing (TQC), a high-impact, peer-reviewed journal that supports the quantum computing community. As the editors-in-chief for TQC, we are delighted to introduce this new journal at a time when quantum computing, and quantum information broadly, are rapidly developing. In recent years, research groups worldwide, as well as both large and small companies, have begun developing quantum computers and computing devices that go beyond the prototype stage toward useful computational tools. The computer science community has already started to understand, evaluate, and build infrastructure around this novel paradigm. Our journal, TQC, is dedicated to providing a central venue for research in this new territory of computer science. The journal aims to publish high-quality papers on both the theory and practice of quantum computing, including but not limited to models of quantum computing, quantum algorithms and complexity, quantum computing architecture, principles and methods of fault-tolerant quantum computation, design automation for quantum computing, issues surrounding compilers for quantum hardware and noisy intermediate-scale quantum implementations, quantum programming languages and systems, distributed quantum computing, quantum networking, quantum security and privacy, and applications (e.g., machine learning and AI) of quantum computing. Quantum computing is interdisciplinary by nature, and the field has been developed from its beginning through the combined effort of researchers from different areas, including computer science, physics, engineering, and mathematics, among many others. We particularly welcome submissions reporting innovative research at the intersection of computer science and these other areas, as well as the application of quantum computing technologies to domains such as quantum simulation, machine learning, and mathematics. We wish to thank the many people who have helped to envision and establish TQC as a highcaliber journal for the quantum community. We are grateful to the members of advisory board for their strong support. We would like to thank our esteemed editorial board members who have joined with enthusiasm in participating in founding this journal. And, of course, we are grateful to the ACM for providing a home for the emerging innovations of quantum computer science. This first issue of TQC presents a collection of five outstanding research papers that capture the breadth and sophistication of quantum computing research. Baker et al. (https://doi.org/10. 1145/3406309) propose a novel technique for decomposition of a large class of quantum circuits that can achieve a significant improvement of depth over the best-known qubit-only techniques. Flammia and Wallman (https://doi.org/10.1145/3408039) present an efficient procedure for characterizing Pauli channels, which are an important noise model in many practical quantum computing architectures. as wel
{"title":"Inaugural Issue Editorial for ACM Transactions on Quantum Computing","authors":"","doi":"10.1145/3411487","DOIUrl":"https://doi.org/10.1145/3411487","url":null,"abstract":"Welcome to the inaugural issue of ACM Transactions on Quantum Computing (TQC), a high-impact, peer-reviewed journal that supports the quantum computing community. As the editors-in-chief for TQC, we are delighted to introduce this new journal at a time when quantum computing, and quantum information broadly, are rapidly developing. In recent years, research groups worldwide, as well as both large and small companies, have begun developing quantum computers and computing devices that go beyond the prototype stage toward useful computational tools. The computer science community has already started to understand, evaluate, and build infrastructure around this novel paradigm. Our journal, TQC, is dedicated to providing a central venue for research in this new territory of computer science. The journal aims to publish high-quality papers on both the theory and practice of quantum computing, including but not limited to models of quantum computing, quantum algorithms and complexity, quantum computing architecture, principles and methods of fault-tolerant quantum computation, design automation for quantum computing, issues surrounding compilers for quantum hardware and noisy intermediate-scale quantum implementations, quantum programming languages and systems, distributed quantum computing, quantum networking, quantum security and privacy, and applications (e.g., machine learning and AI) of quantum computing. Quantum computing is interdisciplinary by nature, and the field has been developed from its beginning through the combined effort of researchers from different areas, including computer science, physics, engineering, and mathematics, among many others. We particularly welcome submissions reporting innovative research at the intersection of computer science and these other areas, as well as the application of quantum computing technologies to domains such as quantum simulation, machine learning, and mathematics. We wish to thank the many people who have helped to envision and establish TQC as a highcaliber journal for the quantum community. We are grateful to the members of advisory board for their strong support. We would like to thank our esteemed editorial board members who have joined with enthusiasm in participating in founding this journal. And, of course, we are grateful to the ACM for providing a home for the emerging innovations of quantum computer science. This first issue of TQC presents a collection of five outstanding research papers that capture the breadth and sophistication of quantum computing research. Baker et al. (https://doi.org/10. 1145/3406309) propose a novel technique for decomposition of a large class of quantum circuits that can achieve a significant improvement of depth over the best-known qubit-only techniques. Flammia and Wallman (https://doi.org/10.1145/3408039) present an efficient procedure for characterizing Pauli channels, which are an important noise model in many practical quantum computing architectures. as wel","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133834028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The famous superdense coding protocol of Bennett and Wiesner demonstrates that it is possible to communicate two bits of classical information by sending only one qubit and using a shared EPR pair. Our first result is that an arbitrary protocol for achieving this task (where there are no assumptions on the sender’s encoding operations or the dimension of the shared entangled state) is locally equivalent to the canonical Bennett-Wiesner protocol. In other words, the superdense coding task is rigid. In particular, we show that the sender and receiver only use additional entanglement (beyond the EPR pair) as a source of classical randomness. We also investigate several questions about higher-dimensional superdense coding, where the goal is to communicate one of d2 possible messages by sending a d-dimensional quantum state, for general dimensions d. Unlike the d=2 case (i.e., sending a single qubit), there can be inequivalent superdense coding protocols for higher d. We present concrete constructions of inequivalent protocols, based on constructions of inequivalent orthogonal unitary bases for all d > 2. Finally, we analyze the performance of superdense coding protocols where the encoding operators are independently sampled from the Haar measure on the unitary group. Our analysis involves bounding the distinguishability of random maximally entangled states, which may be of independent interest.
{"title":"Rigidity of Superdense Coding","authors":"A. Nayak, H. Yuen","doi":"10.1145/3593593","DOIUrl":"https://doi.org/10.1145/3593593","url":null,"abstract":"The famous superdense coding protocol of Bennett and Wiesner demonstrates that it is possible to communicate two bits of classical information by sending only one qubit and using a shared EPR pair. Our first result is that an arbitrary protocol for achieving this task (where there are no assumptions on the sender’s encoding operations or the dimension of the shared entangled state) is locally equivalent to the canonical Bennett-Wiesner protocol. In other words, the superdense coding task is rigid. In particular, we show that the sender and receiver only use additional entanglement (beyond the EPR pair) as a source of classical randomness. We also investigate several questions about higher-dimensional superdense coding, where the goal is to communicate one of d2 possible messages by sending a d-dimensional quantum state, for general dimensions d. Unlike the d=2 case (i.e., sending a single qubit), there can be inequivalent superdense coding protocols for higher d. We present concrete constructions of inequivalent protocols, based on constructions of inequivalent orthogonal unitary bases for all d > 2. Finally, we analyze the performance of superdense coding protocols where the encoding operators are independently sampled from the Haar measure on the unitary group. Our analysis involves bounding the distinguishability of random maximally entangled states, which may be of independent interest.","PeriodicalId":365166,"journal":{"name":"ACM Transactions on Quantum Computing","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122253853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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