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Paper 1

Code switching revisited: Low-overhead magic state preparation using color codes

Lucas Daguerre, Isaac H. Kim

Year

2024

Journal

arXiv preprint

DOI

arXiv:2410.07327

arXiv

2410.07327

We propose a protocol to prepare a high-fidelity magic state on a two-dimensional (2D) color code using a three-dimensional (3D) color code. Our method modifies the known code switching protocol with (i) a recently discovered transversal gate between the 2D and the 3D code and (ii) a judicious use of flag-based postselection. We numerically demonstrate that these modifications lead to a significant improvement in the fidelity of the magic state. For instance, subjected to a uniform circuit-level noise of $10^{-3}$ (excluding idling noise), our code switching protocol yields a magic state encoded in the distance-$3$ 2D color code with a logical infidelity of $4.6\times 10^{-5}\pm 1.6 \times 10^{-5}$ (quantified by an error-corrected logical state tomography) with an $84\%$ of acceptance rate. Used in conjunction with a postselection approach, extrapolation from a polynomial fit suggests a fidelity improvement to $5.1 \times 10^{-7}$ for the same code. Our protocol is aimed for architectures that allow nonlocal connectivity and should be readily implementable in near-term devices. Finally, we also present a simulation technique akin to an extended stabilizer simulator which effectively incorporates the non-Clifford $T$-gate, that permits to simulate the protocol without resorting to a resource intensive state-vector simulation.

Open paper

Paper 2

Trotterless Simulation of Open Quantum Systems for NISQ Quantum Devices

Colin Burdine, Enrique P. Blair

Year

2024

Journal

arXiv preprint

DOI

arXiv:2410.03854

arXiv

2410.03854

The simulation of quantum systems is one of the flagship applications of near-term NISQ (noisy intermediate-scale quantum) computing devices. Efficiently simulating the rich, non-unitary dynamics of open quantum systems remains challenging on NISQ hardware. Current simulation methods for open quantum systems employ time-stepped Trotter product formulas ("Trotterization") which can scale poorly with respect to the simulation time and system dimension. Here, we propose a new simulation method based on the derivation of a Kraus operator series representation of the system. We identify a class of open quantum systems for which this method produces circuits of time-independent depth, which may serve as a desirable alternative to Trotterization, especially on NISQ devices.

Open paper