Researchers set new world record with 14 quantum bits
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In what is being heralded as a major step forward towards quantum computing, Innsbruck physicists have achieved controlled entanglement of 14 quantum bits (qubits) - the largest register that has ever been produced.
"The term entanglement describes a quantum mechanical phenomenon," explained Rainer Blatt from the Institute for Experimental Physics, who led the team. "But while it can clearly be demonstrated experimentally, it is not understood completely. Entangled particles cannot be defined as single particles with defined states but rather as a whole system. By entangling single quantum bits, a quantum computer will solve problems considerably faster than conventional computers. And now our experiment with many particles provides us with new insights into this phenomenon."
Since 2005, the research team has held the record for the number of entangled quantum bits realised experimentally. To date, it believes nobody else has been able to achieve controlled entanglement of eight particles, which represents one quantum byte. Now, the Innsbruck scientists have almost doubled this record. They confined 14 calcium atoms in an ion trap, which, similar to a quantum computer, they then manipulated with laser light. The internal states of each atom formed single qubits and a quantum register of 14qubits was produced. "This register represents the core of a future quantum computer," stated Blatt.
In addition, the physicists also found out that the decay rate of the atoms was not linear, as expected, but proportional to the square of the number of the qubits. "When several particles are entangled, the sensitivity of the system increases significantly," Blatt explained. "This process is known as superdecoherence and has rarely been observed in quantum processing. It is not only of importance for building quantum computers, but also for the construction of precise atomic clocks or carrying out quantum simulations."
To date, the Innsbruck experimental physicists have succeeded in confining up to 64 particles in an ion trap. "Although we have not yet been able to entangle this high number of ions yet, our current findings provide us with a better understanding about the behaviour of many entangled particles and this knowledge may soon enable us to entangle even more atoms," concluded Blatt.
The full findings have been published in the journal Physical Review Letters.
