Surface acoustic wave resonators in the quantum regime

We present systematic measurements of the quality factors of surface acoustic wave (SAW) resonators on ST-X quartz in the gigahertz range at a temperature of 10mK. We demonstrate an internal quality factor Qi approaching 0.5 million at 0.5GHz and show that Qi≥4.0×104 is achievable up to 4.4GHz. We show evidence for a polynomial dependence of propagation loss on frequency, as well as a weak drive power dependence of Qi that saturates at low power, the latter being consistent with coupling to a bath of two-level systems. Our results indicate that SAW resonators are promising devices for integration with superconducting quantum circuits

Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics

We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switchin

Surface acoustic wave devices on bulk ZnO crystals at low temperature

Surface acoustic wave (SAW) devices based on thin films of ZnO are a well established technology. However, SAW devices on bulk ZnO crystals are not practical at room temperature due to the significant damping caused by finite electrical conductivity of the crystal. Here, by operating at low temperatures, we demonstrate effective SAW devices on the (0001) surface of bulk ZnO crystals, including a delay line operating at SAW wavelengths of λ = 4 and 6 μm and a one-port resonator at a wavelength of λ = 1.6 μm. We find that the SAW velocity is temperature dependent, reaching v ≈ 2.68 km/s at 10 mK. Our resonator reaches a maximum quality factor of Qi ≈ 1.5 × 105, demonstrating that bulk ZnO is highly viable for low temperature SAW applications. The performance of the devices is strongly correlated with the bulk conductivity, which quenches SAW transmission above 200 K

Data for the paper "Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics"

dataset for paper J. Rahamim, P. J. Leek, E. Ginossar, and M. H. Szymanska

Coherence and decay of higher energy levels of a superconducting transmon qubit

We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive π pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20  μs for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information

Coherence and decay of higher energy levels of a superconducting transmon qubit

We present measurements of coherence and successive decay dynamics of higher energy levels of a superconducting transmon qubit. By applying consecutive π pulses for each sequential transition frequency, we excite the qubit from the ground state up to its fourth excited level and characterize the decay and coherence of each state. We find the decay to proceed mainly sequentially, with relaxation times in excess of 20  μs for all transitions. We also provide a direct measurement of the charge dispersion of these levels by analyzing beating patterns in Ramsey fringes. The results demonstrate the feasibility of using higher levels in transmon qubits for encoding quantum information