Quantum Logic between Remote Quantum Registers

TL;DR

This paper explores quantum state transfer in solid-state spin systems, analyzing imperfections, proposing a quantum mirror architecture for scalable quantum computing, and demonstrating high-fidelity long-range operations between NV centers.

Contribution

It introduces a comprehensive analysis of quantum state transfer considering realistic imperfections and proposes a novel quantum mirror architecture for scalable quantum computing.

Findings

High fidelity state transfer achievable despite disorder and decoherence.

Dipolar couplings allow for high-fidelity transfer with finite eigenmode lifetime.

Eigenmode-mediated transfer enables robust long-range gates between NV centers.

Abstract

We analyze two approaches to quantum state transfer in solid-state spin systems. First, we consider unpolarized spin-chains and extend previous analysis to various experimentally relevant imperfections, including quenched disorder, dynamical decoherence, and uncompensated long range coupling. In finite-length chains, the interplay between disorder-induced localization and decoherence yields a natural optimal channel fidelity, which we calculate. Long-range dipolar couplings induce a finite intrinsic lifetime for the mediating eigenmode; extensive numerical simulations of dipolar chains of lengths up to L=12 show remarkably high fidelity despite these decay processes. We further consider the extension of the protocol to bosonic systems of coupled oscillators. Second, we introduce a quantum mirror based architecture for universal quantum computing which exploits all of the spins in the system as potential qubits. While this dramatically increases the number of qubits available, the composite operations required to manipulate "dark" spin qubits significantly raise the error threshold for robust operation. Finally, as an example, we demonstrate that eigenmode-mediated state transfer can enable robust long-range logic between spatially separated Nitrogen-Vacancy registers in diamond; numerical simulations confirm that high fidelity gates are achievable even in the presence of moderate disorder.