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Johansen, Lars M. and Luis Aina, Alfredo (2004) Nonclassicality in weak measurements. Physical review A, 70 (5). 052115_1052115_12. ISSN 10502947

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Official URL: http://dx.doi.org/10.1103/PhysRevA.70.052115
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http://journals.aps.org/  Publisher 
Abstract
We examine weak measurements of arbitrary observables where the object is prepared in a mixed state and on which measurements with imperfect detectors are made. The weak value of an observable can be expressed as a conditional expectation value over an infinite class of different generalized Kirkwood quasiprobability distributions. "Strange" weak values for which the real part exceeds the eigenvalue spectrum of the observable can only be found if the TerletskyMargenauHill distribution is negative or, equivalently, if the real part of the weak value of the density operator is negative. We find that a classical model of a weak measurement exists whenever the TerletskyMargenauHill representation of the observable equals the classical representation of the observable and the TerletskyMargenauHill distribution is nonnegative. Strange weak values alone are not sufficient to obtain a contradiction with classical models. We propose feasible weak measurements of photon number of the radiation field. Negative weak values of energy contradict all classical stochastic models, whereas negative weak values of photon number contradict all classical stochastic models where the energy is bounded from below by the zeropoint energy. We examine coherent states in particular and find negative weak values with probabilities of 16% for kinetic energy (or squared field quadrature), 8% for harmonic oscillator energy, and 50% for photon number. These experiments are robust against detector inefficiency and thermal noise.
Item Type:  Article 

Additional Information:  ©2004 The American Physical Society 
Uncontrolled Keywords:  Quantummechanics; Coherent states; Local values; Particle; Optics; Time 
Subjects:  Sciences > Physics > Optics 
ID Code:  31420 
Deposited On:  28 Jul 2015 11:20 
Last Modified:  28 Jul 2015 11:20 
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