Fast Multiqubit Gates through Simultaneous Two-Qubit Gates
Journal article, 2021
Near-term quantum computers are limited by the decoherence of qubits to only being able to run low-depth quantum circuits with acceptable fidelity. This severely restricts what quantum algorithms can be compiled and implemented on such devices. One way to overcome these limitations is to expand the available gate set from single- and two-qubit gates to multiqubit gates, which entangle three or more qubits in a single step. Here, we show that such multiqubit gates can be realized by the simultaneous application of multiple two-qubit gates to a group of qubits where at least one qubit is involved in two or more of the two-qubit gates. Multiqubit gates implemented in this way are as fast as, or sometimes even faster than, the constituent two-qubit gates. Furthermore, these multiqubit gates do not require any modification of the quantum processor, but are ready to be used in current quantum-computing platforms. We demonstrate this idea for two specific cases: simultaneous controlled-Z gates and simultaneous iswap gates. We show how the resulting multiqubit gates relate to other well-known multiqubit gates and demonstrate through numerical simulations that they would work well in available quantum hardware, reaching gate fidelities well above 99%. We also present schemes for using these simultaneous two-qubit gates to swiftly create large entangled states like Dicke and Greenberger-Horne-Zeilinger states.
Author
Xiu Gu
Tencent
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Jorge Fernández-Pendás
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Pontus Vikstål
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Tahereh Abad
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Christopher Warren
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology
Andreas Bengtsson
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology
Giovanna Tancredi
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology
Vitaly Shumeiko
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Jonas Bylander
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology
Göran Johansson
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Anton Frisk Kockum
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
PRX Quantum
26913399 (eISSN)
Vol. 2 4 A202Subject Categories
Computer Engineering
Other Electrical Engineering, Electronic Engineering, Information Engineering
Condensed Matter Physics
DOI
10.1103/PRXQuantum.2.040348