IBM achieves quantum computing milestone

IBM scientists are a step closer to practical quantum computing with the development of new operating, manufacturing and design processes. The company’s researchers have set records for conducting error-free, basic computations and are using microfabrication techniques to create the superconducting chips that form the basis of the technology.

Quantum computing has a wide variety of potential applications, such as cryptography and encryption, where quantum computers could potentially break existing encryption techniques through massive calculations. Other possible uses include searching databases of unstructured information, performing optimization tasks and solving previously unsolvable mathematical problems.

The basic unit of information in quantum computing are quantum bits (qubits), made up of individual atoms. Unlike conventional electronics, whose bits represent either a 0 or a 1, qubits can be in either state or in a third state representing 1 and 0 simultaneously. Known as superposition, this capability potentially allows quantum computers to perform massive computations beyond the scope of conventional computers.

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The challenge is getting data out of this matrix of atoms, which is susceptible to decoherence — losing its quantum state — or being interfered with by electromagnetic radiation.

Error correction in quantum computing allows the qubits to perform for longer periods of time, allowing larger, more complex calculations and operations. IBM is testing an experimental superconducting “three dimensional” qubit (3D qubit) designed to extend the amount to time qubits retain their quantum states.

Researchers have used the 3D qubit to extend the quantum stat up to 100 microseconds — an improvement of 2 to 4 times over previous records, IBM officials said. The 100-microsecond mark is just past the threshold needed to allow effective error correction processes, which permits scientists to focus on scaling up quantum computing processes to permit the future manufacture of thousands or millions of qubits.

The 3D superconducting qubit is about 1 millimeter in length and suspended in the center of a cavity on a sapphire chip. Performance is measured by passing microwave signals to the device’s connectors. IBM officials said that the design team is confident that it can scale up the system to hundreds of thousands of qubits.

IBM researchers also demonstrated a more traditional two-dimensional qubit (2D qubit) device and performed a two-qubit logic operation – a controlled-NOT (CNOT) operation, a fundamental building block for a larger quantum computing system. The operation demonstrated a 95 percent success rate, which was partly enabled due to the long coherence time of nearly 10 microseconds. These numbers are on the cusp of effective error correction schemes and greatly facilitate future multi-qubit experiments, IBM officials said.

"The quantum computing work we are doing shows it is no longer just a brute force physics experiment. It's time to start creating systems based on this science that will take computing to a new frontier," said IBM scientist Matthias Steffen, manager of the research team in a statement.

IBM researchers presented their results at the annual American Physical Society meeting Feb. 27-Mar. 2, 2012, in Boston, Mass.

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