Resonator-based superconducting qubit

Andrew N. Cleland

Quantum bits have been under intense development since the late 1990s, due to the discovery of a number of potential applications for engineered quantum systems to problems in computation or communication. As superconducting circuits provide a straightforward path to scaling up to large numbers of qubits and are exible in terms of their application to a range of different problems, This chapter focuses on the problem of coupling superconducting qubits to other systems, in particular to microwave frequency electromagnetic resonators as well as mechanical resonators. It begins by introducing the topics of piezoelectricity and its role in solid mechanics, then turns to a description of one flavour of superconducting qubit, the phase qubit. It then describes how the phase qubit can be used to control and measure a superconducting electromagnetic resonator, and concludes by describing how a phase qubit can also be used to control and measure a piezomechanical resonator.

Joel Strand

Feng‐Yang Zhang, Wei‐Bin Yan, Chui‐Ping Yang

We study a generalized coupling system between a superconducting qubit and two nanomechanical resonators. When the eigenfrequency of the superconducting qubit is twice the frequency of the resonators, we show that one qubit is able to excite simultaneously two resonators. Moreover, tripartite and bipartite macroscopic entangled states are generated, respectively. We give conditions under which general tripartite and bipartite entangled nonorthogonal states become maximally entangled states. Under a large detuning condition, the coupling between two resonators is induced by a superconducting qubit. This coupling strength can be enhanced via a squeezing transformation.

Alexandre Blais

Frederick W. Strauch, Xiaoting Wang, Kurt A. Jacobs

Walid M. Fahmy, Khalid F. A. Hussein, Abd‐El‐Hadi A. Ammar

This paper proposes a design of a coplanar waveguide resonator (CPWR) to integrate two distant superconducting qubits which is a function required for a quantum information system. In this CPWR, the states of one of the super conducting qubits can be moved to and recovered from the other qubit by microwave resonator photons. The superconducting qubits are relatively straightforward to fabricate from materials such as aluminium using electron beam lithography. The superconducting qubits, which are typically a few hundred micrometres in size, are well suited to perform fast quantum logic gate operations. The CPWR highly couples the two qubits through the tightly confined oscillating magnetic field of the resonator microwave photons. It is shown that, in the proposed CPW resonator structure, the microwave photons can mediate coupling between two distant superconducting qubits (21 mm apart) to realize quantum logic gates.