QUANTUM mechanics describes the world of electrons and atoms, but not everyday objects. What if we could probe the boundaries of this quantum-classical divide by 鈥渆ntangling鈥� two microscopic levers?
Proving that bigger and bigger objects obey the same quantum rules is a huge challenge. Although the cantilevers would be only tens of micrometres long, they would constitute a bigger and more complex system than any yet shown to exhibit quantum behaviour. The larger an object, the more easily its quantum state is destroyed.
In March, Aaron O鈥機onnell and colleagues at the University of California, Santa Barbara, showed that a microscopic cantilever made of aluminium nitride can be simultaneously still and vibrating, a sign that it is in a quantum state.
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Now , Patrik 脰hberg and Chaitanya Joshi of Heriot-Watt University in Edinburgh, UK, and colleagues have a method for entangling two of these microscopic cantilevers.
When two or more objects exist in a 鈥渟uperposition鈥� of linked quantum states, they are said to be entangled. The researchers suggest putting two cantilevers, each with a tiny magnet at its tip, near an ultra-cold ensemble of atoms called a Bose-Einstein condensate. In a BEC all the atoms share the same quantum state. Vibrating one cantilever creates a magnetic field, which causes the atoms in the BEC to move. This motion in turn causes the magnets at the tip of the other cantilever to move, causing the cantilever to vibrate. Under such a system, the two levers should become entangled.
Couple each cantilever to a tiny superconducting coil and the electrical read-out will tell you if their states are correlated more often than classical physics predicts (). 鈥淭he main challenge is to read out the entanglement,鈥� Andersson says.
鈥淢agnetic levers could enter a quantum state 鈥� the main challenge is to read out the entanglement鈥�
at the Ludwig-Maximilians University in Munich, Germany, says this work is 鈥渢he next step鈥� in testing the boundary of quantum behaviour. There are technical challenges to overcome, though. For example, the tip of the cantilever has to be within 250 nanometres of the BEC. 鈥淚t is not at all trivial to get that close.鈥�
