Quantum Cosmology on Quantum Computer

TL;DR

This paper demonstrates the first application of quantum cosmology on physical quantum computers using a novel hybrid quantum-classical algorithm to solve cosmological Hamiltonian constraints with high precision.

Contribution

It introduces a new hybrid quantum-classical algorithm for quantum cosmology and applies it successfully on real quantum hardware, surpassing traditional methods like VQE.

Findings

Achieved approximately 1% error in solving the quantum cosmological constraint.

First demonstration of quantum cosmology computations on physical quantum computers.

Validated the effectiveness of the Hybrid Quantum-Classical algorithm in a cosmological context.

Abstract

With physical quantum computers becoming increasingly accessible, research on their applications across various fields has advanced rapidly. In this paper, we present the first study of quantum cosmology conducted on physical quantum computers, employing a newly proposed Hybrid Quantum-Classical (HQC) algorithm rather than the commonly used Variational Quantum Eigensolver (VQE). Specifically, we solve a constrained Hamiltonian equation derived by quantizing the Friedmann equation in cosmology. To solve this constraint equation, H |psi> = 0, where H is a Hamiltonian operator and |psi> = |psi(theta)> is the wave function of phase angle theta describing the cosmic quantum state, we iteratively use the quantum computer to compute the eigenvalues of <psi | H | psi>, while a classical computer manages the underlying probability density function within the Probabilistic Bisection Algorithm (PBA) to update theta until the solution of <psi | H | psi> = 0 is achieved to a desired accuracy. Executing our algorithm on IBM's quantum computers, we attain a high-precision solution for theta, achieving approximately 1 percent error.