Scientists develop powerful method of suppressing errors in quantum computers

April 23rd, 2009 - 4:26 pm ICT by ANI  

Washington, April 23 (ANI): Scientists at the National Institute of Standards and Technology (NIST) have demonstrated a technique for efficiently suppressing errors in quantum computers.

The advance could eventually make it much easier to build useful versions of these potentially powerful but highly fragile machines, which theoretically could solve important problems that are intractable using today’s computers.

The new error-suppression method was demonstrated using an array of about 1,000 ultracold beryllium ions (electrically charged atoms) trapped by electric and magnetic fields.

Each ion can act as a quantum bit (qubit) for storing information in a quantum computer.

These ions form neatly ordered crystals, similar to arrays of qubits being fabricated by other researchers using semiconducting and superconducting circuitry.

Arrays like this potentially could be used as multi-bit quantum memories.

The new NIST technique counteracts a major threat to the reliability of quantum memories: the potential for small disturbances, such as stray electric or magnetic fields, to create random errors in the qubits.

The NIST team applied customized sequences of microwave pulses to reverse the accumulation of such random errors in all qubits simultaneously.

“Simulations show that under appropriate conditions this method can reduce the error rate in quantum computing systems up to a hundred times more than comparable techniques. Our measurement results validate these predictions,” said Hermann Uys, a NIST guest researcher.

According to co-lead author Michael J. Biercuk, a NIST post-doc, correcting qubit errors after they occur will require extraordinary resources, whereas early suppression of errors is far more efficient, and improves the performance of subsequent error correction.

The new NIST error-suppression method could enable quantum computers of various designs to achieve error rates far below the so-called fault-tolerance threshold of about 1 error in 10,000 computational operations (0.01 percent), he added.

If error rates can be reduced below this level, building a useful quantum computer becomes considerably more realistic.

Quantum computers, by relying on the unusual properties of the atomic-scale world to store and process data, could someday break commonly used encryption codes, perform faster searches of enormous databases, and determine the most efficient schedules for everything from airlines to traveling salespeople.

They could also simulate complex quantum systems that are too difficult to study using today’s computers or through direct experiments. (ANI)

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