Three-qubit entangling gates with simultaneous exchange controls in spin qubit systems

TL;DR

This paper introduces multi-qubit entangling gates using simultaneous exchange controls in spin qubit systems, reducing circuit complexity and enhancing efficiency for quantum computing.

Contribution

It presents analytical expressions and implementation strategies for multi-exchange three-qubit gates, enabling more efficient quantum circuit construction in spin qubit systems.

Findings

Multi-qubit gates reduce the number of elementary operations.

Constructed circuits can generate GHZ, W, and Toffoli states.

Enhanced efficiency and coherence in spin-qubit quantum circuits.

Abstract

Pairwise exchange couplings have long been the standard mechanism for entangling spin qubits in semiconductor systems. However, implementing quantum circuits based on pairwise exchange gates often requires a lengthy sequence of elementary gate operations. In this work, we present an alternative approach: multi-qubit entangling gate operations that simultaneously drive the exchange couplings between multiple pairs of spin qubits. We explore three spin qubit systems in linear or triangular configurations. We derive analytical expressions for these multi-exchange entangling operations and demonstrate how to use the resulting three-qubit gates to construct quantum circuits capable of generating standard entangled states such as GHZ and W states, and the Toffoli gate, by optimizing control parameters. Our results show that this multi-qubit strategy significantly reduces the number of required operations, offering a pathway to more efficient, shallower, and more coherent circuits for spin-qubit processors.