Figure 1: Qubit circuit and experimental procedure.
From: Tunable quantum beam splitters for coherent manipulation of a solid-state tripartite qubit system
(a) Schematic of the qubit circuitry. Josephson junctions Al/AlOx/Al are denoted by the X symbols. The flux bias, microwave and readout dc-SQUID are inductively coupled to the qubit with inductance L≈770 pH, capacitance C≈240 fF and critical current I0≈1.4 μA. (b) Principle of the operation and measurement of the phase qubit. The two lowest eigenstates, |0
and |1, form the qubit with transition frequency ω10, which can be adjusted by changing the flux bias. A microwave pulse is used to manipulate the qubit state and readout pulse and then lower the potential energy barrier to perform a fast single-shot readout. (c) Schematic of a two-level state located inside the insulating tunnel barrier of a Josephson junction and its eigenstates in different bases. (d) Spectroscopy of the coupled qubit–TLS system with corresponding quantum states labelled. Two avoided crossings centered at ωTLS1 and ωTLS2 are observed.
