Measuring the temperature dependence of individual two-level systems by direct coherent control

Abstract

We demonstrate a new method to directly manipulate the state of individual two-level systems (TLS) in phase qubits. It allows one to characterize the coherence properties of TLS using standard microwave pulse sequences, while the qubit is used only for state readout. We apply this method to measure the temperature dependence of TLS coherence for the first time. The energy relaxation time $T_1$ is found to decrease quadratically with temperature for the two TLS studied in this work, while their dephasing time measured in Ramsey and spin-echo experiments is found to be $T_1$ limited at all temperatures.

4 pages, 5 figures

References in corpus (5)

• State tomography of capacitively shunted phase qubits with high fidelity
• Quantum two-level systems in Josephson junctions as naturally formed qubits
• Temperature dependence of coherent oscillations in Josephson phase qubits
• Multi-photon spectroscopy of a hybrid quantum system
• Relaxation of Josephson qubits due to strong coupling to two-level systems