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A quantum logic gate between a solid-state quantum bit and a photon


Integrated nanophotonic devices create strong light–matter interactions that are important for the development of solid-state quantum networks1, distributed quantum computers2 and ultralow-power optoelectronics3,4. A key component for many of these applications is the photonic quantum logic gate, where the quantum state of a solid-state quantum bit (qubit) conditionally controls the state of a photonic qubit. These gates are crucial for the development of robust quantum networks5,6,7, non-destructive quantum measurements8,9 and strong photon–photon interactions10. Here, we experimentally realize a quantum logic gate between an optical photon and a solid-state qubit. The qubit is composed of a quantum dot strongly coupled to a nanocavity, which acts as a coherently controllable qubit system that conditionally flips the polarization of a photon on picosecond timescales, implementing a controlled-NOT gate. Our results represent an important step towards solid-state quantum networks and provide a versatile approach for probing quantum dot–photon interactions on ultrafast timescales.

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Figure 1: Implementation of a quantum dot–photon cNOT operation.
Figure 2: Device characterizations under c.w. excitation.
Figure 3: Demonstration of controlled bit flip by pulsed pump–probe excitation.
Figure 4: cNOT operations for all four combinations of input–output polarizations.


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The authors acknowledge support from the Army Research Office Multidisciplinary University Research Initiative on hybrid quantum interactions (grant no. W911NF09104), a Defense Advanced Research Projects Agency (DARPA) Defense Science Office grant (grant no. W31P4Q0910013), the Physics Frontier Center at the Joint Quantum Institute, and the Office of Naval Research Applied Electromagnetics Center. E.W. acknowledges support from the National Science Foundation Faculty Early Career Development (CAREER) award (grant no. ECCS 0846494) and a DARPA Young Faculty Award (grant no. N660011114121).

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Authors and Affiliations



H.K. and E.W. conceived and designed the experiment, and prepared the manuscript. H.K. carried out the measurements and analysed the data. R.B. and T.C.S. contributed to the measurements and sample design. E.W. and H.K. carried out the theoretical analysis. G.S.S. provided samples grown by molecular beam epitaxy.

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Correspondence to Edo Waks.

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The authors declare no competing financial interests.

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Kim, H., Bose, R., Shen, T. et al. A quantum logic gate between a solid-state quantum bit and a photon. Nature Photon 7, 373–377 (2013).

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