updated 01:05 pm EST, Tue February 28, 2012
Research brings quantum computers one step closer
Scientists at IBM labs have established three new records in the field of quantum computing, bringing the reality of a practical, full-scale quantum computer one step closer. The researchers discovered new methods for for reducing errors due to quantum decoherence in elementary computations and retaining the integrity of quantum mechanical properties. The researchers will present their results at the annual American Physical Society meeting taking place February 27-March 2, 2012 in Boston.
The attraction of quantum computing is simple: quantum computers can work on millions of computations at once, many times faster than even the fastest supercomputers. The prospect of additional computational power is especially relevant to the the field of data encryption, where quantum computers could factor very large numbers like those used to decode and encode sensitive information. Other uses may include searching databases of unstructured information, performing optimization tasks and solving previously unsolvable mathematical problems.
The basic unit that carries information within quantum computing is referred to as a quantum bit (qubit). Binary computers can use information stored as either as "1" or "0." Quantum computers rely on the property of superposition, which is the ability of a qubit to be either "1," "0," or both simultaneously.
Part of the challenge of quantum computing is the instability caused by interference from factors such as heat, electromagnetic radiation, and materials defects. This phenomenon is known as quantum decoherence. To perform complex calculations, qubits need to retain their quantum mechanical properties long enough to employ error correction schemes.
IBM Labs' research focuses on superconducting qubits, which use established microfabrication techniques and should allow a more facile transition to scale up and manufacturing.
IBM's latest experiment involves a "three dimensional" superconducting qubit (3D qubit), building on work initiated at Yale University. One of the experiments extends the amount of time that the qubits retain their quantum states up to 100 microseconds. That interval is two to four times as long as the previous record, and approaches the threshold necessary for effective error correction schemes. The team believes a stable 3D qubit system could possibly scale up to hundreds or thousands of qubits.
The team also investigated a a controlled-NOT (CNOT) operation with a more typical two-dimensional qubit device. The CNOT function is a fundamental building block of a larger quantum computing system. The team used a three qubit device to achieve a coherence time of nearly 10 microseconds. That period is near the point that a quantum computing system would require for effective error correction methods.
A picture of IBM's "3D" superconducting qubit device where a qubit (about 1mm in length) is suspended in the center of the cavity on a small Sapphire chip.
A picture of the Silicon chip housing a total of three qubits. The chip is back-mounted on a PC board and connects to I/O coaxial lines via wire bonds. (scale: 8mm x 4mm)