Entangled quantum clocks for measuring proper-time dierence

Abstract. We report that entangled pairs of quantum clocks (non-degenerate quantum bits) can be used as a specialized detector for precisely measuring dierence of proper-times that each constituent quantum clock experiences. We describe why the proposed scheme would be more precise in the measurement of proper-time dierence than a scheme of two-separate-quantum-clocks. We consider possibilities that the proposed scheme can be used in precision test of the relativity theory. PACS. 03.67.-a Quantum information { 06.30.Ft Time and frequency { 04.80.Cc Experimental tests of gravitational theories It is quantum entanglement that led to the historical con-troversy over Einstein-Podolsky-Rosen experiment [1] and then led to the Bell’s inequality [2] that explicitly re-vealed non-local nature of quantum mechanics. On the other hand, entanglement is the key ingredient in quan-tum information processing: for example, the speedup in quantum computation [3] is obtained through the paral-lel quantum operations on massively superposed state