Distributed Quantum Computation Based-on Small Quantum Registers

TL;DR

This paper presents a hybrid quantum computation scheme using small quantum registers connected via probabilistic optical links, achieving high-fidelity non-local gates despite high local error rates.

Contribution

It introduces a novel register-based scheme with probabilistic entanglement, a two-level pumping method for high-fidelity Bell pairs, and a Markov chain model for entanglement pumping analysis.

Findings

Deterministic non-local gates with high fidelity are achievable despite high local error rates.

A new two-level pumping scheme can create Bell pairs with arbitrarily high fidelity.

The scheme's fault-tolerance requirements are discussed, including an alternative GHZ state preparation method.

Abstract

We describe and analyze an efficient register-based hybrid quantum computation scheme. Our scheme is based on probabilistic, heralded optical connection among local five-qubit quantum registers. We assume high fidelity local unitary operations within each register, but the error probability for initialization, measurement, and entanglement generation can be very high (~5%). We demonstrate that with a reasonable time overhead our scheme can achieve deterministic non-local coupling gates between arbitrary two registers with very high fidelity, limited only by the imperfections from the local unitary operation. We estimate the clock cycle and the effective error probability for implementation of quantum registers with ion-traps or nitrogen-vacancy (NV) centers. Our new scheme capitalizes on a new efficient two-level pumping scheme that in principle can create Bell pairs with arbitrarily high fidelity. We introduce a Markov chain model to study the stochastic process of entanglement pumping and map it to a deterministic process. Finally we discuss requirements for achieving fault-tolerant operation with our register-based hybrid scheme, and also present an alternative approach to fault-tolerant preparation of GHZ states.