Fast preparation of highly-entangled quantum states

Abstract

A method of preparing an entangled state of a plurality of qubits. The method comprises: (i) preparing an array of qubits, each qubit being in a ground qubit state and having an excited qubit state. The array comprises a plurality of first qubits and a plurality of second qubits, each first qubit disposed at a vertex of a first lattice, each second qubit disposed at a vertex of a second lattice, wherein each first qubit has at least one nearest neighbor second qubit, wherein for any two first qubits, a spacing between said first qubits and their respective nearest neighbor second qubits is the same, each first qubit capable of having an Ising interaction with its nearest neighbor second qubit; (ii) causing a single-site rotation of the plurality of the first qubits and of the plurality of the second qubits, thereby causing each first and each second qubit to transition into a superposition of the ground qubit state and the excited qubit state; (iii) evolving the array of qubits for a pre-determined time τ, thereby producing a cluster state of the array of qubits; and (iv) measuring the state of each first qubit, wherein the measuring comprises reversing the single-site rotation of the plurality of the first qubits, thereby preparing an entangled state of the plurality of second qubits.