New work asserts that a key technique used to probe quantum systems may not be so quantum after all, according to postdoctoral researcher Joshua Combes and his colleague Christopher Ferrie.
Over the past 20 years, a strange idea called a “weak value” has taken root in quantum information science.
From NIST Tech Beat: September 15, 2014
Researchers at the Institute for Quantum Computing at the University of Waterloo in Canada have directly entangled three photons in the most technologically useful state for the first time, thanks in part to superfast, super-efficient single-photon detectors developed by the National Institute of Standards and Technology (NIST).
1- Photon number discrimination without photon counting (theory and experiment)
The chromatic number of a graph has a description as the classical value of a three-person game. If instead one plays a quantum version of this game, then this yields a smaller value--the quantum chromatic number of the graph. However, using the Algebraic Quantum Field Theory (AQFT) model could yield a larger set of quantum correlations, and a different value for the quantum chromatic number.
The conventional electronic devices such as personal computers and mobile phones are primarily based on the control of electron charge in semiconductors. Although the tremendous progress in micro-fabrication technologies has accelerated the miniaturization of electronic devices, the size of devices will soon encounter the fundamental physical limits of that miniaturization. Further scale reduction beyond these limits will require a radical alteration of the concept of functional devices.
The conventional electronic devices such as personal computer and mobile phones are primarily based on the control of electron charge in semiconductors. Although the tremendous progress in micro-fabrication technologies has accelerated the miniaturization of electronic devices, the size of devices will soon encounter the fundamental physical limits of that miniaturization. Further scale reduction beyond these limits will require a radical alteration of the concept of functional devices.
As a standard method for producing correlated photon pairs (biphotons), spontaneous parametric down-conversion in nonlinear crystal usually has a wide bandwidth (terahertz) and very short coherence time (pico-seconds). Within spontaneous four-wave mixing process in cold atom ensembles, here we present a method for producing narrow-band (megahertz) Stokes and anti-Stokes paired photons.
Digital signatures ensure that messages cannot be forged or tampered with. They are widely used to provide security for electronic communications, for example in financial transactions and electronic mail. Importantly, signed messages are also transferrable, meaning that if one recipient accepts a message as genuine, then she is guaranteed that others will also accept the same message if it is forwarded.
In practical applications of communication schemes it is often necessary to amplify the transmitted signals. Because of the intrinsic noise due to Heisenberg's uncertainty principle, a quantum signal requires an amplification process which is different than the one used for classical signals.