Distributing entanglement between distant semiconductor qubit registers using a shared-control shuttling link

TL;DR

This paper demonstrates a novel method for distributing entanglement between distant semiconductor qubit registers using a shared-control shuttling link, advancing modular quantum computing with germanium hole spin qubits.

Contribution

It introduces the first shared-control shuttling link between distant qubit registers, enabling entanglement generation in a modular quantum processor.

Findings

Successful entanglement of distant spin qubits in separate registers.

Fast qubit shuttling over micrometer distances within 100 nanoseconds.

Implementation of a protocol to counteract spin-orbit effects during transfer.

Abstract

Semiconductor quantum processors have potential to scale to modular quantum computers, in which qubit registers are coupled by quantum links, enabling high connectivity and space for control circuitry. Individual spin-qubit registers have progressed to two-dimensional systems and execution of small quantum algorithms. Separately, high-fidelity spin shuttling has been demonstrated in linear channels defined by individual gate electrodes. Here, we realize the first shared-control shuttling link integrated between distant qubit registers to demonstrate quantum entanglement in a basic modular quantum processor based on hole spin qubits in germanium. We develop a protocol to compensate for spin-orbit-induced rotations during qubit transfer, allowing for shuttling between qubit registers separated by more than one micrometer in approximately a hundred nanoseconds. Combining local qubit operation with coherent shuttling, we generate Bell states formed by spins residing in separate registers. Characterizing them using quantum state tomography, we demonstrate entanglement between spin qubits in distant registers.