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Measurement of time by quantum clocks
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1980
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EngineeringQuantum MeasurementUnstable AtomClock SynchronizationQuantum SensingQuantum ClockMeasurement ProblemTime DisseminationQuantum ComputingTemporal DynamicQuantum EntanglementTemporalityTimed SystemQuantum SciencePhysicsQuantum InformationNatural SciencesTemporal ComplexityQuantum AnalogTiming SystemsQuantum DevicesQuantum Clocks
A clock is a dynamical system that progresses through states at regular intervals, enabling measurement of process durations, recording of events, and control of process timing. The paper demonstrates how to construct time‑independent Hamiltonians to model quantum clock applications. High‑time resolution demands large energy exchange that alters the system’s evolution, and an overly precise clock can even freeze the evolution, illustrating a quantum Zeno effect.
A clock is a dynamical system which passes through a succession of states at constant time intervals. If coupled to another system, it can measure the duration of a physical process and even keep a permanent record of it, such as in a time-of-flight experiment or in observing the lifetime of an unstable atom. A clock can also be used to control the duration of a process, e.g., the precession of a spin in a magnetic field which is turned on and off at prescribed times. This article shows how to construct time-independent Hamiltonians describing these possible uses of a quantum clock. As expected, a good time resolution entails a large energy exchange between the clock and the other system, thereby modifying the evolution of the latter. This evolution may even be halted by using a clock which is too precise (this is the quantum analog of Zeno’s paradox).