Gate-error analysis in simulations of quantum computers with transmon qubits

The real-time dynamics of systems with up to three SQUIDs is studied by numerically solving the time-dependent Schrödinger equation. The numerical results are used to scrutinize the mapping of the flux degrees of freedom onto two-level systems (the qubits) as well as the performance of the intermediate SQUID as a tunable coupling element. It is shown that the two-level representation yields a good description of the flux dynamics during quantum annealing, and the presence of the tunable coupling element does not have negative effects on the overall performance. Additionally, data obtained from a two-level spin dynamics simulation of quantum annealing is compared to experimental data produced by the D-Wave 2000Q quantum annealer. The effects of finite temperature are incorporated in the simulation by coupling the qubit-system to a bath of spin-1/2 particles. It is shown that including an environment modeled as non-interacting two-level systems that couple only to the qubits can produce data which matches the experimental data much better than the simulation data of the isolated qubits, and better than data obtained from a simulation including an environment modeled as interacting two-level systems coupling to the qubits.

show abstract

“…This is definitely different from the errors caused by the resonators in the considered gate-based model in Ref. [2].…”

Section: B Comparison To the Two-level Systemmentioning

confidence: 64%

“…The set {S k } of variables that minimize Eq. (2) give the solution of the QUBO. Quantum annealing can, at least in principle, find (one of) the ground state(s) of the Ising-spin Hamiltonian Eq.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Real-time simulation of flux qubits used for quantum annealing

Willsch

Jin

et al. 2020

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

“…Compared with quantum process tomography [18,19], RB is resource-efficient, and robust against state preparation and measurement errors. Simple to implement, RB has been used in a large variety of experiments, from benchmarking gate performances [4,8,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] to creative uses like partial tomography and quantum control [40][41][42][43][44][45].…”

Section: Huimentioning

confidence: 99%

Comparing the randomized benchmarking figure with the average infidelity of a quantum gate-set

2019

Int. J. Quantum Inform.

View full text Add to dashboard Cite

Randomized benchmarking (RB) is a popular procedure used to gauge the performance of a set of gates useful for quantum information processing (QIP). Recently, Proctor et al. [Phys. Rev. Lett. 119, 130502 (2017)] demonstrated a practically relevant example where the RB measurements give a number r very different from the actual average gate-set infidelity , despite past theoretical assurances that the two should be equal. Here, we derive formulas for , and for r from the RB protocol, in a manner permitting easy comparison of the two. We show in general that, indeed, r = , i.e., RB does not measure average infidelity, and, in fact, neither one bounds the other. We give several examples, all plausible in real experiments, to illustrate the differences in and r. Many recent papers on experimental implementations of QIP have claimed the ability to perform high-fidelity gates because they demonstrated small r values using RB. Our analysis shows that such a statement from RB alone has to be interpreted with caution.

show abstract

“…For remote users, it may undermine the assumption of trusted operations -preparation, memory or measurement -that quantum verification [12] or quantum key distribution protocols [13] rely on to guarantee their security. Leakage has been studied in some detail in specific quantum computing platforms [14][15][16][17][18]. General frameworks have been developed, but rely on certain assumptions.…”

Section: Introductionmentioning

confidence: 99%

Quantum leakage detection using a model-independent dimension witness

2019

View full text Add to dashboard Cite

Users of quantum computers must be able to confirm they are indeed functioning as intended, even when the devices are remotely accessed. In particular, if the Hilbert space dimension of the components are not as advertised -for instance if the qubits suffer leakage -errors can ensue and protocols may be rendered insecure. We refine the method of delayed vectors, adapted from classical chaos theory to quantum systems, and apply it remotely on the IBMQ platform -a quantum computer composed of transmon qubits. The method witnesses, in a model-independent fashion, dynamical signatures of higher-dimensional processes. We present evidence, under mild assumptions, that the IBMQ transmons suffer state leakage, with a p value no larger than 5×10 −4 under a single qubit operation. We also estimate the number of shots necessary for revealing leakage in a two-qubit

show abstract

Gate-error analysis in simulations of quantum computers with transmon qubits

Cited by 49 publications

References 54 publications

Real-time simulation of flux qubits used for quantum annealing

Real-time simulation of flux qubits used for quantum annealing

Comparing the randomized benchmarking figure with the average infidelity of a quantum gate-set

Quantum leakage detection using a model-independent dimension witness

Contact Info

Product

Resources

About