Optical-transition atomic clock beyond the standard quantum limit
Abstract
Optical~transition atomic clock beyond the standard quantum limitVladan Vuletic, MITAbstractState-of-the-art atomic clocks or other precision interferometers operate at or near the standardquantum limit, where the instrument precision improves as the square root of the participatingparticle number. The standard quantum limit is a consequence of the projection postulate whereeach atom is ultimately measured in one of two quantum states. This discretization ofmeasurement results leads to quantum noise even when all technical and thermal noise has beenremoved. The standard quantum limit can be overcome by using entangled states, wherecorrelations between different atoms can reduce the effect of quantum noise on the measurement.The simplest such entangled states are spin squeezed states where the quantum noise remainsGaussian, but is redistributed so as to reduce the phase noise of the atomic clock, therebyimproving clock performance. Previous spin squeezing has reached the level of 17dB (implyinga potential factor of 50 in reduction in averaging time for a given desired precision), but allexperiments so far have been performed in clocks with poor absolute performance that wasseveral orders of magnitude below that of state-of-the art systems.It is proposed to demonstrate operation below the standard quantum limit for the first time in astate-of-the-art atomic clock that uses an optical transition. Spin squeezing will be implementedin an ensemble of ytterbium atoms. It will be established optically between two magneticsublevels in the electronic ground state, and then transferred onto the clock transition by meansof a laser pulse. It is expected that spin squeezing will improve the clock stability by a factor ofmore than 10 over the standard quantum limit, and that the clock can be operated at a precisionbetter than 1 part in 10^16 in one second.Instead of reducing the quantum noise, entangled states can also be used to effectively increasethe signal frequency. It is proposed to generate Schroedinger cat states via the strong coupling ofthe ensemble to an optical resonator. The phase evolution speed of such states is larger than thatof individual atoms, which can be used to overcome the standard quantum limit. Furthermore,the application of entangled states to an atom interferometer will be explored.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 03, 2017
- Source ID
- N000141712254
Entities
People
- Vladan Vuletić
Organizations
- Massachusetts Institute of Technology
- Office of Naval Research
- United States Navy