N. J. Lambert, M. Edwards, A. A. Esmail, F. A. Pollock, S. D. Barrett, B. W. Lovett, A. J. Ferguson
Superconductivity relies on a correlated ground state composed of entangled electrons called Cooper-pairs. If an individual Cooper-pair can be controllably broken up into its two component quasiparticles, it could form a key resource of entanglement for quantum information processing applications. Electrical devices that split Cooper-pairs, with the resulting electrons comprising a spatially separated pair of output currents, have been proposed and realised. By contrast, we demonstrate a splitter where the component quasiparticles are delivered to a pair of localized and controllable superconducting quantum dots, and we detect both the splitting and recombination of individual Cooper-pairs. We anticipate that such a superconducting double quantum dot geometry will enable single spin measurement of quasiparticles, and a resulting quantum processor would benefit from their long spin coherence times, as recently measured in superconducting aluminium. Moreover, we show that these single Cooper-pairs can be intentionally split by applying a microwave ?field, thus demonstrating a broadband, tuneable threshold `click-detector' for single photons of microwave light.
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http://arxiv.org/abs/1304.5117
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