QUANTUM BIT is represented by the presence or absence of a pair of superconducting electrons in a "box" of aluminum. The gold "wings" collect stray unpaired electrons; the red port sends in microwave pulses to "write" the qubit. Image: QUANTRONICS-DSM-CEA
In the race for quantum computers, researchers would love to sculpt quantum bits, or qubits, with existing chip-manufacturing techniques. Qubits are able to exist as both 0 and 1 at once. But the same wires that would make qubit chips easy to manipulate and link together also connect them to the quantum-defiling messiness of the outside world. So far no one has figured out how to make the 0/1 superposition last very long in circuit form.
Three different research teams, however, have made critical breakthroughs. In May the Quantronics group at the Atomic Energy Commission (CEA) in Saclay, France, and Siyuan Han's laboratory at the University of Kansas reported qubit chip designs with coherence times at least 100 times as great as those achieved before. Investigators at the National Institute of Standards and Technology (NIST) in Boulder, Colo., have come up with a design that they think could yield similar coherence rates. "What people are beginning to understand is how to build circuits so that these qubits aren't coupled to noise and dissipation," says NIST physicist John M. Martinis.
This article was originally published with the title Coherent Computing.