Abstract
An on-demand single-photon source is a key element in a series of prospective quantum technologies and applications. Here we demonstrate the operation of a tuneable on-demand microwave photon source based on a fully controllable superconducting artificial atom strongly coupled to an open-ended transmission line. The atom emits a photon upon excitation by a short microwave π-pulse applied through a control line. The intrinsically limited device efficiency is estimated to be in the range 65–80% in a wide frequency range from 7.75 to 10.5 GHz continuously tuned by an external magnetic field. The actual demonstrated efficiency is also affected by the excited state preparation, which is about 90% in our experiments. The single-photon generation from the single-photon source is additionally confirmed by anti-bunching in the second-order correlation function. The source may have important applications in quantum communication, quantum information processing and sensing.
Highlights
Control and manipulation with light at the single-photon level [1,2,3,4] is interesting from fundamental and practical viewpoints
We propose and realise a different approach: a single-photon source based on a tuneable artificial atom coupled asymmetrically to two open-end transmission lines (1D half-spaces)
The following are intrinsic features of the device: (i) The two lines are well isolated from each other so that the excitation pulse does not leak from the control line to the emission line; (ii) due to the strong asymmetry, the excited atom emits a photon with up to 1−(Cc/Ce)2 probability; (iii) the photon is confined in the 1D transmission line and can be delivered to other circuit elements through the line
Summary
Cuits coupled to 1D transmission lines [16,17,18]. Fig. 1c shows a circuit with an artificial atom coupled asymmetrically to a pair of open-end coplanar transmission lines (1D-half spaces), each with Z = 50 Ω impedance. A MW pulse is applied from the control line, exciting the atom, and the atom emits a photon mainly to the emission line due to asymmetric coupling: Ce/Cc ≈ 5. In the ideal case of suppressed pure dephasing (γ = 0) and in the absence of nonradiative decay Γn1r = 0, the power ratio between the control and emission lines generated by the atom under resonance is |Vc(0, t)/Ve(0, t)|2 = Cc2/Ce2 ≈ 0.04, which means that up to 96% of the power generated by the atom can be emitted into the emission line We evaluate the efficiency of our source over a wide frequency range by tuning the emission frequency ω10
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