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Macroscopic non-classical states and terahertz quantum processing in room-temperature diamond


The nature of the transition between the familiar classical, macroscopic world and the quantum, microscopic one continues to be poorly understood. Expanding the regime of observable quantum behaviour to large-scale objects is therefore an exciting open problem1. In macroscopic systems of interacting particles, rapid thermalization usually destroys any quantum coherence before it can be measured or used at room temperature2. Here, we demonstrate quantum processing in the vibrational modes of a macroscopic diamond sample under ambient conditions. Using ultrafast Raman scattering, we create an extended, highly non-classical state in the optical phonon modes of bulk diamond. Direct measurement of phonon coherence and correlations establishes the non-classical nature of the crystal dynamics. These results show that optical phonons in diamond provide a unique opportunity for the study of large-scale quantum behaviour, and highlight the potential for diamond as a micro-photonic quantum processor capable of operating at terahertz rates.

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Figure 1: Raman quantum memory and decoherence measurement in diamond.
Figure 2: Non-classical correlations in the quantum memory.
Figure 3: Population and coherence of non-classical phonons versus read–write delay.


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This work was supported by the QIPIRC (Quantum Information Processing Interdisciplinary Research Collaboration) and EPSRC (Engineering and Physical Sciences Research Council) (grant no. GR/S82176/01), EU ITN (European Union International Training Network) EMALI (Engineering, Manipulation and Characterization of Quantum States of Matter and Light), EU IP (Integrated Project) Q-ESSENCE (Quantum Interfaces, Sensors, and Communication based on Entanglement), EU ITN FASTQUAST (Ultrafast Control of Quantum Systems by Strong Laser Fields), Toshiba Research Europe, Clarendon Fund, NSERC (Natural Sciences and Engineering Research Council of Canada), and a Royal Society/Wolfson Research Merit Award. The authors are grateful to S. Prawer for useful discussions.

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K.C.L. built the experiment with assistance from B.J.S. and M.R.S. and collected the data. K.C.L., B.J.S. and J.N. contributed to the theoretical analysis. K.F.R., P.M., N.K.L., P.J.B. and D.J. provided useful insights, and I.A.W. and B.J.S. conceived the experiment. The manuscript was written by K.C.L. with input from B.J.S., J.N., N.K.L., M.R.S. and I.A.W.

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Correspondence to B. J. Sussman or I. A. Walmsley.

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The authors declare no competing financial interests.

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Lee, K., Sussman, B., Sprague, M. et al. Macroscopic non-classical states and terahertz quantum processing in room-temperature diamond. Nature Photon 6, 41–44 (2012).

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