Quantum Clock Synchronization with one qubit

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The clock synchronization problem is to determine the time difference T between two spatially separated parties. We improve on I. Chuang's quantum clock synchronization algorithm and show that it is possible to obtain T to n bits of accuracy while communicating only one qubit in one direction and using an O(2ⁿ) frequency range. We also prove a quantum lower bound of Ω(2ⁿ) for the product of the transmitted qubits and the range of frequencies, thus showing that our algorithm is optimal.