A dynamical implementation of canonical second quantization on a quantum computer

TL;DR

This paper introduces a new method for implementing creation and annihilation operators in quantum computers, enabling dynamic particle mode management with improved qubit efficiency over traditional approaches.

Contribution

It develops a formalism for second quantization on quantum computers that allows for variable particle number and more efficient qubit encoding compared to Jordan-Wigner.

Findings

Provides theorems for commutation and anticommutation relations on finite memory

Derives formulae for unitary evolution with multi-body Hamiltonians

Achieves qubit scaling of order n log2 Np, more efficient than Jordan-Wigner for certain cases

Abstract

We develop theoretical methods for the implementation of creation and destruction operators in separate registers of a quantum computer, allowing for a transparent and dynamical creation and destruction of particle modes in second quantization in problems with variable particle number. We establish theorems for the commutation (anticommutation) relations on a finite memory bank and provide the needed symmetrizing and antisymmetrizing operators. Finally, we provide formulae in terms of these operators for unitary evolution under conventional two- and four-body Hamiltonian terms, as well as terms varying the particle number. In this formalism, the number of qubits needed to codify $n$ particles with $N_p$ modes each is of order $n\log_2 N_p$. Such scaling is more efficient than the Jordan-Wigner transformation which requires $O(N_p)$ qubits, whenever there are a modest number of particles with a large number of states available to each (and less advantageous for a large number of particles with few states available to each). And although less efficient, it is also less cumbersome than compact encoding.