Hybrid spin-superconducting quantum circuit mediated by deterministically prepared entangled photonic states

Abstract

In hybrid quantum systems a controllable coupling can be obtained by mediating the interactions with dynamically introduced photons. We propose a hybrid quantum architecture consisting of two nitrogen vacancy center ensembles coupled to a tunable flux qubit; that are contained on the transmission line of a multimode nonlinear superconducting coplanar waveguide resonator with an appended Josephson mixing device. We discuss using entangled propagating microwaves photons, which through our nonlinear wave-mixing procedure are made into macroscopically distinct quantum states. We use these states to steer the system and show that with further amplification we can create a similar photonic state, which has a more distinct reduction of its uncertainty. Furthermore, we show that all of this leads to a lengthened coherence time, a reasonable fidelity which decays to 0.94 and then later increases upward to stabilize at 0.6 as well as a strengthened entanglement.Hybrid quantum systems have emerged as a potential solution, due to the properties which the interface between the different components can provide as an open quantum system. 1,2 Nitrogen vacancy center ensembles (NVEs) have been of importance due to their ability to be coupled and their stability in an open system. [3][4][5][6][7][8] Various studies have been done involving them collectively coupled to a flux qubit (FQ). 9-11 This coupling can be extended beyond the strong coupling regime to ultrastrong domains. 12 But, with the addition of more qubits the system would not be completely robust.We use a modified superconducting coplanar waveguide resonator (CWR) as a multimode microwave photon quantum bus, [13][14][15][16] to which we apply quantum reservoir engineering, to create two-mode entangled microwave fields as the interaction medium. The microwave fields can be affected by the decoherence from the surrounding qubits, which make them less effective in transferring states within the system. One way to strengthen both the system and the microwave fields and make them less susceptible to dissipation is through transforming them into nonclassical states, 17-19 such as a coherent superposition state or Schrödinger cat state. 20 We look at the degree of squeezing applied and attempt to extend the work of Minganti et al. 21 and Hacker et al. 22 , which suggested the inherent squeezing of coherent cat states and a method of deterministically generating cat states. 23 We look at a Schrödinger cat-like state, which in our system. This state has been explored because of its ability to suppress noise, which can lead to more precise measurements, such as in quantum enhanced sensing. 24 In our study, we look at cases involving a systematic creation and distribution of coherent and squeezed coherent macroscopically distinct states by the multimode parametric waveguide 25-29 , and compare their functions and the resulting system metrics to make a comparison between them.The system under consideration as illustrated in Figure 1, contains two nitrogen-vacancy center ensemble...

Evaluation of highly entangled states in asymmetrically coupled three NV centers by quantum simulator

“…In some irregular configurations a strong resonant tunnelling can be found from the strong entanglement or a right combination of states as observed by breaking the symmetry of a regular configuration. These special structures would be useful to develop NV center based hybrid quantum devices [31] also by adding squeezed states obtained from strong coupling between a resonator and a couple of NV centers [32]. These closed loop configurations of NV centers can be useful for the development of spin qubits and topological qubits.…”