Researchers from Australia and Japan have recently reported a successful attempt at quantum teleportation of a complex quantum system from a certain point A to another point B without losing information. The team was led by scientists from the University of Tokyo, in the lab of Professor Akira Furusawa. This leads to the possibility of achieving fast, high-fidelity transmission of huge chunks of data, all at once, thus revolutionising the current data transportation scenario and providing a boost to the ongoing research on quantum computers.
Schrodinger and his Cat
The Schrodinger Cat paradox appeared in 1934 and was proposed by Erwin Schrodinger, one of the founders of quantum theory. This thought experiment (‘gedankenexperiment‘) consists of the following setup: A cat is kept in an opaque box with a sealed glass chamber inside it, containing poisonous gas. The glass can be broken by a hammer, which is itself triggered by the decay of a radioactive atom. Since the decay of any radioactive atom is governed by quantum laws and is, thus, entirely probabilistic, no one can say whether the cat is alive or dead with absolute certainty. The answer, however, becomes obvious when one looks into the box. Before the observation, one is forced to conclude that the cat is dead and alive at the same time; it is in a superposition of dead’ and alive’ states. Thus, observation changes the system irreversibly; scientists call it collapse’.
Whereas quantum superposition and collapse are well-accepted by physicists, applying them to macroscopic objects like cats instead of quantum particles makes the situation very strange. The strangeness enticed Schrodinger enough to propose this paradox.
Teleportation, Qubits and the Quantum Computer
The concept of superposition is employed in quantum computers. Unlike a conventional computer, where one bit can have the value 0 or 1, a quantum bit (or qubit) can be in a superposition of the two values. Thus, when there are N bits it represents only one state, where N qubits represent 2N states at once. This greatly augments both speed and volume of computations.
The main problem in achieving quantum computers is that the qubits are highly susceptible to external influences. As discussed above, observing a qubit (i.e. any interaction with the environment) will collapse it into one of the many states that it represents. Thus, a number of qubits cannot be stacked up at a place, unlike computer bits. (Currently, 10 qubits have been ‘stacked’ up.)
Another phenomenon used is that of quantum entanglement. If two states are conjoined at some time, then the observation on one of the states influences the other, even though the latter is not being directly observed. This finds a (hitherto hypothetical) application, which involves performing one operation on a certain part of the computer and, thus, influencing a separate entangled operation. This concept can be exploited in quantum cryptography.
The Japanese team of researchers have successfully teleported a macroscopic system of photons (particles of light), whose phases were superposed.
Are quantum computers just round the corner?