Implementation of a Quantum Switch with Superconducting Circuits: Part 1 - Theory

A quantum switch (QSwitch) is a four-node quantum router that swaps a single photon between an input and two outputs based on a quantum address. In contrast to previous quantum routers, which require the output qubit to be classically selected, a QSwitch can route to a superposition of outputs. A QSwitch is a necessary component for building a quantum RAM (QRAM), as the gate that it enables forms the basis of the memory access operation upon which QRAM usage relies.

This is the first part of a two-part talk. In this part we will focus on a new protocol that relies on a strong ZZ coupling between a control qubit and the input and output qubits. We will show that this protocol is much more gate efficient. We will also show how this design can be efficiently scaled to design a QRAM.