Noisy Intermediate-Scale Quantum (NISQ) Computers: How They Work, How They Fail, How to Test Them? Sebastian Brandhofer; Simon Devitt; Thomas Wellens and Ilia Polian. In Proceedings of the 39th IEEE VLSI Test Symposium (VTS’21), Virtual, 2021, pp. 1--6.
Zusammenfassung
First quantum computers very recently have demonstrated “quantum supremacy” or “quantum advantage”: Executing a computation that would have been impossible on a classical machine. Today’s quantum computers follow the NISQ paradigm: They exhibit error rates that are much higher than in conventional electronics and have insufficient quantum resources to support powerful error correction protocols. This raises questions which relevant computations are within the reach of NISQ architectures. Several “NISQ-era algorithms” are assumed to match the specifics of such computers; for instance, variational optimisers are based on intertwining relatively short quantum and classical computations, thus maximizing the chances of success. This paper will critically assess the promise and challenge of NISQ computing. What has this field achieved so far, what are we likely to achieve soon, where do we have to be skeptical and wait for the advent of larger-scale fully error-corrected architectures?BibTeX
ArsoNISQ: Analyzing Quantum Algorithms on Near-Term Architectures. Sebastian Brandhofer; Simon Devitt and Ilia Polian. In Proceedings of the 26th IEEE European Test Symposium (ETS’21), Virtual, 2021, pp. 1--6.
Zusammenfassung
While scalable, fully error corrected quantum computing is years or even decades away, there is considerable interest in noisy intermediate-scale quantum computing (NISQ). In this paper, we introduce the ArsoNISQ framework that determines the tolerable error rate of a given quantum algorithm computation, i.e. quantum circuits, and the success probability of the computation given a success criterion and a NISQ computer. ArsoNISQ is based on simulations of quantum circuits subject to errors according to the Pauli error model. ArsoNISQ was evaluated on a set of quantum algorithms that can incur a quantum speedup or are otherwise relevant to NISQ computing. Despite optimistic expectations in recent literature, we did not observe quantum algorithms with intrinsic robustness, i.e. algorithms that tolerate one error on average, in this evaluation. The evaluation demonstrated, however, that the quantum circuit size sets an upper bound for its tolerable error rate and quantified the difference in tolerate error rates for quantum circuits of similar sizes. Thus, the framework can assist quantum algorithm developers in improving their implementation and selecting a suitable NISQ computing platform. Extrapolating the results into the quantum advantage regime suggests that the error rate of larger quantum computers must decrease substantially or active quantum error correction will need to be deployed for most of the evaluated algorithmsBibTeX
Optimal Mapping for Near-Term Quantum Architectures based on Rydberg Atoms. Sebastian Brandhofer; Hans Peter Büchler and Ilia Polian. In To appear in Proceedings of the 40th IEEE International Conference On Computer-Aided Design (ICCAD’21), Munich, Germany, 2021, pp. 1--6.
Zusammenfassung
Quantum algorithms promise quadratic or exponential speedups for applications in cryptography, chemistry and material sciences. The topologies of today's quantum computers offer limited connectivity, leading to significant overheads for implementing such quantum algorithms. One-dimensional topology displacements that remedy these limits have been recently demonstrated for architectures based on Rydberg atoms, and they are possible in principle in photonic and ion trap architectures. We present the first optimal quantum circuit-to-architecture mapping algorithm that exploits such one-dimensional topology displacements. We benchmark our method on quantum circuits with up to 15 qubits and investigate the improvements compared with conventional mapping based on inserting swap gates into the quantum circuits. Depending on underlying technology parameters, our approach can decrease the quantum circuit depth by up to 58\% and increase the fidelity by up to 29\%. We also study runtime and fidelity requirements on one-dimensional displacements and swap gates to derive conditions under which one-dimensional topology displacements provide benefits.BibTeX