New “quantum distillation” method allows measuring coherence of quantum states
UAB researchers have come up with a method that allows measuring the strength of the coherence of superposition in any given quantum state, similar to the famous Schrödinger's cat, which was simultaneously dead and alive. For the first time ever, the method can be used in any given quantum state in superposition.
![Coherence](/Imatge/566/270/coherenceweb,0.gif)
In the article, researchers from the UAB Department of Physics Andreas Winter and Dong Yang propose a groundbreaking method to measure the strength of coherence in any given quantum state. The researchers created simple formulas to calculate how much "pure coherence" is contained in a given quantum state, by answering two fundamental questions: How efficiently can one transform the state into "pure coherence"? And how efficient is the reverse process?
"At first the quantum state must be distilled. We must see how much coherence can be extracted from it", explains Andreas Winter, to later "once again form a state of 'noise' in which the coherence is diluted". The distillation and dilution process allows measuring the strength of the coherence of the initial state of superposition with experiments which can be tailored to each particular case. This is an outstanding contribution to the study of quantum physics given that “traditionally, to measure the degree of coherence of a superposition it was necessary to be able to measure the visibility of interference fringes, linked to standardised experiments”, Winter highlights. “Our approach, in contrast, adapts to all states since it can design an experiment tailored to specific needs.”
The research, conducted by researchers from the Quantum Information Group at the UAB Department of Physics Andreas Winter (ICREA researcher), and Dong Yang, also member of the Laboratory for Quantum Information of Jiliang University Hangzhou in Zhejiang, China, has been published this week in the journal Physical Review Letters.
Original article:
Operational Resource Theory of Coherence, Andreas Winter and Dong Yang, Phys. Rev. Lett. 116, 120404. http://dx.doi.org/10.1103/PhysRevLett.116.120404