Spin Qubit Leapfrogging: Dynamics of shuttling electrons on top of another

TL;DR

This paper proposes a novel method for shuttling spin qubits over stationary electrons using valley degrees of freedom in silicon, enabling new routing and entangling operations in quantum processors.

Contribution

It introduces a leapfrogging technique that leverages valley states to shuttle electrons over stationary qubits, expanding mobility and operation possibilities.

Findings

Simulations demonstrate the feasibility of leapfrogging spin qubits.

The method enables implementation of a SWAP$^ extgamma$ entangling gate.

Proposes a new approach to handle low valley splitting regions in silicon.

Abstract

Spin shuttling has crystalized as a powerful and promising tool for establishing intermediate-range connectivity in semiconductor spin-qubit devices. Although experimental demonstrations have performed exceptionally well on different materials platforms, the question of how to handle areas of low valley splitting in silicon during shuttling remains unresolved. In this work, we explore the possibility of utilizing the valley degree of freedom, particularly in regions of low valley splitting, to allow mobile spin qubits to be shuttled through an occupied stationary quantum dot, thereby leapfrogging over the stationary electron. This not only grants a more enriched mobility for shuttled electrons, as it opens new possible routing paths, but also enables the implementation of an entangling SWAP$^\gamma$ two-qubit gate operation in the process. Simulating this process for different sets of parameters, we demonstrate the feasibility of such an operation and offer a unique use case for otherwise precarious regions of a quantum processor chip and propose a possible extension to the set of possible operations for silicon spin qubit devices.