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Fast reset and suppressing spontaneous emission of a superconducting qubit
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View: Figures


Image of FIG. 1.
FIG. 1.

Design, realization, and diagnostic transmission data of the Purcell filter. (a) Circuit model of the Purcell-filtered cavity design. The Purcell filter, implemented with twin open-circuited transmission-line stubs, inhibits decay through near its resonance . (b) Optical micrograph of the device with inset zoom on transmon qubit. Note the correspondence of the circuit elements directly above in (a). (c) Cavity transmission measured at 4.2 K and comparison to the circuit-model prediction. The Purcell filter shorts out the output environment at , yielding a 30 dB drop in transmission (arrow). A circuit model involving only the parameters , , , and shows excellent correspondence.

Image of FIG. 2.
FIG. 2.

Qubit as a function of frequency measured with two methods and comparison to various models. The first method is a static measurement (circles): the qubit is excited and measured after a wait time . The second (triangles) is a dynamic measurement: the qubit frequency is tuned with a fast flux pulse to an interrogation frequency, excited, and allowed to decay for , and then returned to its operating frequency of 5.16 GHz and measured. This method allows for accurate measurement even when is extremely short. Measurements using the two methods show near perfect overlap. The top dashed curve is the predicted , while solid curve includes also nonradiative internal loss with best-fit . The two lower curves correspond to an unfiltered device with the same , , and , with and without the internal loss. In this case, the Purcell filter gives a improvement by up to a factor of (6.7 GHz).

Image of FIG. 3.
FIG. 3.

Fast qubit reset. (a) Schematic of a pulse sequence used to realize a qubit reset and characterize its performance. The fidelity of reset was quantified using a modified Rabi oscillation scheme. The qubit is first rotated around the -axis by an angle at the operating frequency of 5.16 GHz and then pulsed into near resonance with the cavity (solid line) or left at the operating frequency (dashed line) for a time . The state of the qubit is measured as a function of and after being pulsed back to 5.16 GHz. (b) The Rabi-oscillation amplitude as a function of , normalized to the amplitude for . This ratio gives the deviation of the qubit state from equilibrium. Curves are fit to exponentials with decay constants of and , respectively. Insets: Measured Rabi oscillations for (lower left) and (top right). The vertical scales differ by a factor of 100.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Fast reset and suppressing spontaneous emission of a superconducting qubit