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In 1967, Simon Kochen and Ernst Specker proved mathematically that even for a single quantum object, where entanglement is not possible, the values that you obtain when you measure its properties depend on the context. So the value of property A, say, depends on whether you chose to measure it with property B, or with property C. In other words, there is no reality independent of the choice of measurement. It wasn't until 2008, however, that Alexander Klyachko of Bilkent University in Ankara, Turkey, and colleagues devised a feasible test for this prediction. They calculated that if you repeatedly measured five different pairs of properties of a quantum particle that was in a superposition of three states, the results would differ for the quantum system compared with a classical system with hidden variables. That's because quantum properties are not fixed, but vary depending on the choice of measurements, which skews the statistics. "This was a very clever idea," says Anton Zeilinger of the Institute for Quantum Optics, Quantum Nanophysics and Quantum Information in Vienna, Austria. "The question was how to realise this in an experiment." Now he, Radek Lapkiewicz and colleagues have realised the idea experimentally. They used photons, each in a superposition in which they simultaneously took three paths. Then they repeated a sequence of five pairs of measurements on various properties of the photons, such as their polarisations, tens of thousands of times. A beautiful experiment They found that the resulting statistics could only be explained if the combination of properties that was tested was affecting the value of the property being measured. "There is no sense in assuming that what we do not measure about a system has [an independent] reality," Zeilinger concludes.

'Quantum information technology is a field of physics aimed at harnessing some of the deepest phenomena in physics to create wholly new forms of technology, such as computers and communication systems,' said Erik Gauger of Oxford University's Department of Materials, an author of the paper.

Entropy can decrease, according to a new proposal - but the process would destroy any evidence of its existence, and erase any memory an observer might have of it. It sounds like the plot to a weird sci-fi movie, but the idea has recently been suggested by theoretical physicist Lorenzo Maccone, currently a visiting scientist at MIT, in an attempt to solve a longstanding paradox in physics.

With this new experiment, the researchers have succeeded for the first time in experimentally reconstructing full trajectories which provide a description of how light particles move through the two slits and form an interference pattern. Their technique builds on a new theory of weak measurement that was developed by Yakir Aharonov's group at Tel Aviv University. Howard Wiseman of Griffith University proposed that it might be possible to measure the direction a photon (particle of light) was moving, conditioned upon where the photon is found. By combining information about the photon's direction at many different points, one could construct its entire flow pattern ie. the trajectories it takes to a screen.