Sep 21, 2012 |
Light squeezed on a quantum scale
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(Nanowerk News) An international team of physicists has pushed the boundaries on ultra-precise measurement by harnessing quantum light waves in a new way.
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It is one thing to be able to measure spectacularly small distances using "squeezed" light, but it is now possible to do this even while the target is moving around.
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An Australian-Japanese research collaboration made the breakthrough in an experiment conducted at the University of Tokyo, the results of which have been published in an article, "Quantum-enhanced optical phase tracking" in the prestigious journal, Science.
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Leader of the international theoretical team Professor Howard Wiseman, from Griffith University's Centre for Quantum Dynamics, said this more precise technique for motion tracking will have many applications in a world which is constantly seeking smaller, better and faster technology.
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"At the heart of all scientific endeavour is the necessity to be able to measure things precisely," Professor Wiseman said.
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"Because the phase of a light beam changes whenever it passes through or bounces off an object, being able to measure that change is a very powerful tool."
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"By using squeezed light we have broken the standard limits for precision phase tracking, making a fundamental contribution to science," he said. "But we have also shown that too much squeezing can actually hurt."
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Dr Dominic Berry from Macquarie University has been collaborating with Professor Wiseman on the theory of this problem for many years.
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"The key to this experiment has been to combine "phase squeezing" of light waves with feedback control to track a moving phase better than previously possible," Dr Berry said.
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"Ultra-precise quantum-enhanced measurement has been done before, but only with very small phase changes. Now we have shown we can track large phase changes as well," he said.
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Professor Elanor Huntington from UNSW Canberra, who directed the Australian experimental contribution, is a colleague of Professor Wiseman in the Centre for Quantum Computation and Communication Technology.
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"By using quantum states of light we made a more precise measurement than is possible through the conventional techniques using laser beams of the same intensity," Professor Huntington said.
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Curiously, we found that it is possible to have too much of a good thing. Squeezing beyond a certain point actually degrades the performance of the measurement making it less precise than if we had used light with no squeezing."
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