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You don't need to set the universe in a spin to see time travel in action – so what happened when a photon with a quantum gun went back to kill itself? CHATTING about time travel in a room overlooking a verdant quadrangle at the Massachusetts Institute of Technology seems strangely appropriate. The building dates from 1916 and looks its age: the high ceilings, echoing corridors and musty offices with heavy wooden doors have changed little in that time.
ABSOLUTE zero sounds like an unbreachable limit beyond which it is impossible to explore. In fact there is a weird realm of negative temperatures that not only exists in theory, but has also proved accessible in practice. An improved way of getting there, outlined last week, could reveal new states of matter.
Back in 1970, a young physicist working in the Soviet Union made a counterintutive prediction. Vitaly Efimov, now at the University of Washington in the US, showed that quantum objects that cannot form into pairs could nevertheless form into triplets. In 2006, a group in Austria found the first example of such a so-called Efimov state in a cold gas of cesium atoms.
A delayed choice quantum eraser , first performed by Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. Shih, and Marlan O. Scully , [ 1 ] and reported in early 1999, is an elaboration on a quantum eraser experiment involving the concepts considered in Wheeler's delayed choice experiment .
A man sits down before a gun , which is pointed at his head. This is no ordinary gun; it's rigged to a machine that measures the spin of a quantum particle . Each time the trigger is pulled, the spin of the quantum particle -- or quark -- is measured.
When people don't like what science tells them, they resort to conspiracy theories, mud-slinging and plausible pseudoscience – as Einstein discovered "THIS world is a strange madhouse," remarked Albert Einstein in 1920 in a letter to his close friend, the mathematician Marcel Grossmann. "Every coachman and every waiter is debating whether relativity theory is correct. Belief in this matter depends on political affiliation."
Jamie Condliffe, reporter (Image: Linden Gledhill / Cognisys ) Is it a robo-hedgehog?