Large flux-mediated coupling in hybrid electromechanical system with a transmon qubit

Abstract

Control over the quantum states of a massive oscillator is important for several technological applications and to test the fundamental limits of quantum mechanics. Addition of an internal degree of freedom to the oscillator could be a valuable resource for such control. Recently, hybrid electromechanical systems using superconducting qubits, based on electric-charge mediated coupling, have been quite successful. Here, we show a hybrid device, consisting of a superconducting transmon qubit and a mechanical resonator coupled using the magnetic-flux. The coupling stems from the quantum-interference of the superconducting phase across the tunnel junctions. We demonstrate a vacuum electromechanical coupling rate up to 4 kHz by making the transmon qubit resonant with the readout cavity. Consequently, thermal-motion of the mechanical resonator is detected by driving the hybridized-mode with mean-occupancy well below one photon. By tuning qubit away from the cavity, electromechanical coupling can be enhanced to 40 kHz. In this limit, a small coherent drive on the mechanical resonator results in the splitting of qubit spectrum, and we observe interference signature arising from the Landau-Zener-Stückelberg effect. With improvements in qubit coherence, this system offers a platform to realize rich interactions and could potentially provide full control over the quantum motional states.

Quantum Control via Landau-Zener-Stückelberg-Majorana Transitions

“…Because this is needed for LZSM interferometry, the solution is to create dressed states by applying a microwave signal; then, the slow driving would result in traversing these dressed states around the avoided-level crossing. LZSM interference was realized by several groups with the following features: driven by sinusoidal and noisy signals (Li et al, 2013), performing a time-resolved state tomography measurement (Gong et al, 2016b), resolving multi-photon processes (Chang et al, 2020) with variable coupling between the qubit and the transmission line (Wen et al, 2020), and coupling to a mechanical resonator (Bera et al, 2021).…”

Mechanical frequency control in inductively coupled electromechanical systems

“…Here, vacuum coupling rates have reached the widely reported limit of 300 Hz 8 – 11 and effects such as ground state cooling 12 , strong coupling 6 , 13 , state transfer 14 , mechanical squeezing 15 , as well as electromechanically induced transparency effects 7 , 16 – 18 have been reported. Only recently, the concept of inductive coupling, where the mechanical displacement is transduced into a change of the resonator inductance and hence resonance frequency, has been demonstrated 19 – 22 . This concept offers the potential to significantly increase the single-photon coupling rate beyond the above-mentioned limit 8 – 11 , 23 .…”

Optomechanical Anti-Lasing with Infinite Group Delay at a Phase Singularity

“…In the microwave domain, OMIT [56][57][58][59][60] and OMIA [61][62][63][64] have been demonstrated in electromechanical devices where a superconducting microwave resonator couples to a mechanical resonator realized as a capacitor [65][66][67]. Integrating electromechanics with solid-state qubits, e.g., superconducting qubits [68][69][70][71][72], leads to a promising hybrid architecture for a quantum repeater [73]. The parametric optomechanical coupling has a great tunability.…”