nSQUID arrays as conveyers of quantum information

Abstract

We have considered the quantum dynamics of an array of nSQUIDs -two-junction SQUIDs with negative mutual inductance between their two arms. Effective dual-rail structure of the array creates additional internal degree of freedom for the fluxons in the array, which can be used to encode and transport quantum information. Physically, this degree of freedom is represented by electromagnetic excitations localized on the fluxon. We have calculated the spatial profile and frequency spectrum of these excitations. Their dynamics can be reduced to two quantum states, so that each fluxons moving through the array carries with it a qubit of information. Coherence properties of such a propagating qubits in the nSQUID array are characterized by the dynamic suppression of the lowfrequency decoherence due to the motion-induced spreading of the noise spectral density to a larger frequency interval.

Suppression of Dephasing by Qubit Motion in Superconducting Circuits

“…The most straightforward way of achieving this transfer is to physically move the quantum states representing the qubits of information along the circuit. In the case of superconducting qubits, potential for such a direct motion of logical qubits is offered by so-called negative-inductance SQUIDs [8,9], but operation of these circuits in the quantum regime [10] still needs to be demonstrated experimentally. Another method of transferring logical qubits between different physical qubits, already developed in experiments and adopted in this work, is based on creating controlled qubit-qubit interaction through coupling to a common resonator bus [5,[11][12][13]] (see Fig.…”

Beyond Moore’s technologies: operation principles of a superconductor alternative

“…However, this imposes certain restriction on the circuit design. It is interesting to note that it was proposed to use nSQUID circuits for the implementation of “flying qubits” transmitting quantum information [ 73 , 76 ]. Yet, this idea is not implemented experimentally.…”

Fluxon-based quantum simulation in circuit QED

“…Even a relatively simple circuit implementation of this model, with four lattice sites, displays a spectrum including a pair of edge states, which could be used to implement a superconducting qubit. Finally, we note that beyond the scope of quantum simulation, the concept of quantum fluxonics could be appealing for on-chip quantum state transfer [73,74], or for quantum signal routing using traveling fluxons [75].…”