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Quantum-enhanced positioning and clock synchronization


A wide variety of positioning and ranging procedures are based on repeatedly sending electromagnetic pulses through space and measuring their time of arrival. The accuracy of such procedures is classically limited by the available power and bandwidth. Quantum entanglement and squeezing have been exploited in the context of interferometry1,2,3,4,5, frequency measurements6, lithography7 and algorithms8. Here we report that quantum entanglement and squeezing can also be employed to overcome the classical limits in procedures such as positioning systems, clock synchronization and ranging. Our use of frequency-entangled pulses to construct quantum versions of these protocols results in enhanced accuracy compared with their classical analogues. We describe in detail the problem of establishing a position with respect to a fixed array of reference points.

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Figure 1: Sketch of the idealized experimental configuration.
Figure 2: Sensitivity to loss.


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This work was funded by the ARDA, NRO, and by ARO under a MURI program.

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Correspondence to Seth Lloyd.

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Giovannetti, V., Lloyd, S. & Maccone, L. Quantum-enhanced positioning and clock synchronization. Nature 412, 417–419 (2001).

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