Superconducting Analogues of Quantum Optical Phenomena: Macroscopic Quantum Superpositions and Squeezing in a SQUID Ring

Abstract

In this paper we explore the quantum behaviour of a SQUID ring which has a significant Josephson coupling energy. We show that that the eigenfunctions of the Hamiltonian for the ring can be used to create macroscopic quantum superposition states of the ring. We also show that the ring potential may be utilised to squeeze coherent states. With the SQUID ring as a strong contender as a device for manipulating quantum information, such properties may be of great utility in the future. However, as with all candidate systems for quantum technologies, decoherence is a fundamental problem. In this paper we apply an open systems approach to model the effect of coupling a quantum mechanical SQUID ring to a thermal bath. We use this model to demonstrate the manner in which decoherence affects the quantum states of the ring.

9 pages, 10 figures, To be submitted to Phys. Rev. A. (changes for referee's and editior's comments - replaced to try to get PDF working)

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• Experimental motivation and empirical consistency in minimal no-collapse quantum mechanics
• A size criterion for macroscopic superposition states
• Protecting entanglement in superconducting qubits
• Cool for Cats
• Dynamical model selection near the quantum-classical boundary
• Heat cost of parametric generation of microwave squeezed states
• Insufficiency of avoided crossings for witnessing large-scale quantum coherence in flux qubits
• Entanglement of qubits via a nonlinear resonator
• Quantum chaos in the mesoscopic device for the Josephson flux qubit
• Parity-assisted generation of nonclassical states of light in circuit quantum electrodynamics
• Energy Down Conversion between Classical Electromagnetic Fields via a Quantum Mechanical SQUID Ring
• Resonant effects in a SQUID qubit subjected to non adiabatic changes