Distributed Quantum Computing and Network Control for Accelerated VQE

TL;DR

An approach for distributing the accelerated variational quantum eigensolver algorithm over arbitrary sized—in terms of number of qubits—distributed quantum computers and an architecture for a distributed quantum control system in the context of centralized and decentralized network control are considered.

Abstract

Interconnecting small quantum computers will be essential in the future for creating large scale, robust quantum computers. Methods for distributing monolithic quantum algorithms efficiently are thus needed. In this work we consider an approach for distributing the accelerated variational quantum eigensolver (AVQE) algorithm over arbitrary sized - in terms of number of qubits - distributed quantum computers. We consider approaches for distributing qubit assignments of the Ansatz states required to estimate the expectation value of Hamiltonian operators in quantum chemistry in a parallelized computation and provide a systematic approach to generate distributed quantum circuits for distributed quantum computing. Moreover, we propose an architecture for a distributed quantum control system in the settings of centralized and decentralized network control.

Figures (17)

• Figure 1: An example of a dataflow program.
• Figure 2: Circuit diagram for a non-local CNOT gate between $\ket{\psi_1}$ and $\ket{\psi_2}$ where (a) is the Cat-Entangler sequence and (b) the Cat-Disentangler sequence.
• Figure 3: Distribution of a 11-qubit Ansatz on three QPUs with 6 qubits each. One qubit is reserved for $\alpha$-QPE in green. Communication qubits are reserved in orange. The Ansatz qubits are in red. Two qubits are reserved for communication to accommodate for any control-control gates that could occur when running $\alpha$-QPE that need to cross QPUs.
• Figure 4: Circuit diagram for QPE with unitary operation $U$ and eigenstate $\ket\psi$.
• Figure 5: Circuit diagram for RFPE. $Z(M\theta) \coloneqq \text{diag}(1,e^{-iM\theta})$.

Theorems & Definitions (1)

• Definition 2: Schedule