Strong Coupling of a Spin Ensemble to a Superconducting Resonator

Abstract

We report the realization of a quantum circuit in which an ensemble of electronic spins is coupled to a frequency tunable superconducting resonator. The spins are nitrogen-vacancy centers in a diamond crystal. The achievement of strong coupling is manifested by the appearance of a vacuum Rabi splitting in the transmission spectrum of the resonator when its frequency is tuned through the nitrogen-vacancy center electron spin resonance.

Magnetic field resilient superconducting fractal resonators for coupling to free spins

“…After sputtering a 200 nm thick niobium film, the resonators were patterned using electron beam lithography and subsequent etching in a CF 4 : O 2 (20:1) plasma. Measurements were performed in a helium flow cryostat and a dilution refrigerator using a vector network analyzer to measure the transmitted microwave signal, S 21 .…”

“…[1][2][3] Recently, an ensemble of spins embedded in a crystal has become a subject of quantum manipulation by interaction with a superconducting resonator. 4,5 Spin systems are very promising quantum objects since their coherence times can be very long. However, the magnetic field required to bring free-electron spins into resonance with microwave field exceeds many times the field a standard coplanar waveguide (CPW) resonator can withstand.…”

Microwave transitions as a signature of coherent parity mixing effects in the Majorana-transmon qubit

“…The properties of solid-state qubits and resonators and coupling to photons can be engineered to some degree by design and this enables the combination of several different subsystems to form hybrid devices that take advantage of their relative strengths 9,10 . In turn, this leads to new methods of probing physical systems and, where highly quantum coherent subsystems are involved, to establishing control over their quantum variables.…”

Hybrid quantum circuit consisting of a superconducting flux qubit coupled to a spin ensemble and a transmission-line resonator

“…(20), the effective coupling strength g eff is estimated to be g eff ∼ 10 MHz, which is comparable to the direct-coupling strength between 10 12 NV centers and the transmission-line resonator (a recent experiment is in Ref. 38). The low decay rates from the cavity (κ ∼ 1 MHz), the flux qubit (γ Q ∼ 1MHz), and the spin ensemble (1 < γ S < 10 MHz) have been implemented in recent experiments.…”

“…11 Note that the NV center can also couple to the magnetic field in the transmission-line resonator. 38 However, compared with the magnetic field produced by the current in the qubit loop, this magnetic field is much weaker because of the reasons below: First, the current in the central line of the transmission-line resonator is usually smaller (about one order of magnitude or more smaller) than the current in the qubit loop. Second, a closed loop with a static current can produce a stronger magnetic field than the magnetic field at the same distance…”