Powerful quantum computer made with superconducting ‘artificial atoms’ is possible
March 2, 2005 | Source: KurzweilAI
Two superconducting devices have been coaxed into a special, interdependent state that mimics the unusual interactions sometimes seen in pairs of atoms, an important step toward the possible use of “artificial atoms” made with superconducting materials for storing and processing data in an ultra-powerful quantum computer of the future.
Optical micrograph showing an "artificial atom" made with a superconducting circuit. The red arrow points to the heart of the qubit -- the Josephson junction device that might be used in a future quantum computer to represent a 1, 0, or both values at once.
Research using real atoms as qubits has advanced rapidly, but superconducting circuits offer the advantage of being easily manufactured, easily connected to each other, easily connected to existing integrated circuit technology, and mass producible using semiconductor fabrication techniques.
The work reported in Science creates qubits from superconducting circuit elements called Josephson junctions.
The scientists measured the state of a superconducting qubit by applying a voltage pulse lasting 5 nanoseconds and detecting a change in magnetic field through a simple transformer coil incorporated in the qubit. To detect the tiny variations in the magnetic field, they used a superconducting quantum interference device (SQUID). If a signal is detected, the qubit is in the 1 (or excited) state; if no signal is detected the qubit is in the 0 state.
Through very precise timing, the team also was able to measure the two qubits simultaneously. This was key to avoid unwanted measurement crosstalk that destroys quantum information. The scientists were able to witness a pattern of quantum oscillations that is consistent with the entanglement needed for producing quantum logic gates.