Coherent quantum state storage and transfer between two phase qubits via a resonant cavity

TL;DR

This paper demonstrates coherent quantum state transfer between two superconducting qubits via a resonant cavity, showing potential for scalable quantum communication and memory in quantum processors.

Contribution

It provides the first experimental demonstration of quantum state transfer between two superconducting qubits through a resonant cavity, advancing scalable quantum network architecture.

Findings

Quantum state transfer achieved between two qubits via a resonant cavity

Quantum information stored and retrieved as nonclassical photon states

Superconducting cavity can serve as long-term quantum memory

Abstract

A network of quantum-mechanical systems showing long lived phase coherence of its quantum states could be used for processing quantum information. As with classical information processing, a quantum processor requires information bits (qubits) that can be independently addressed and read out, long-term memory elements to store arbitrary quantum states, and the ability to transfer quantum information through a coherent communication bus accessible to a large number of qubits. Superconducting qubits made with scalable microfabrication techniques are a promising candidate for the realization of a large scale quantum information processor. Although these systems have successfully passed tests of coherent coupling for up to four qubits, communication of individual quantum states between qubits via a quantum bus has not yet been demonstrated. Here, we perform an experiment demonstrating the ability to coherently transfer quantum states between two superconducting Josephson phase qubits through a rudimentary quantum bus formed by a single, on chip, superconducting transmission line resonant cavity of length 7 mm. After preparing an initial quantum state with the first qubit, this quantum information is transferred and stored as a nonclassical photon state of the resonant cavity, then retrieved at a later time by the second qubit connected to the opposite end of the cavity. Beyond simple communication, these results suggest that a high quality factor superconducting cavity could also function as a long term memory element. The basic architecture presented here is scalable, offering the possibility for the coherent communication between a large number of superconducting qubits.