A Canadian company called D:Wave has the best claim to be making and selling quantum computers. Now a research team at Canada’s Simon Fraser University has announced that it has held a quantum memory state stable at room temperature for 39 minutes. This is 100 times longer than the previous record, and it has got the scientific community excited.
In conventional computers, “bits” of data are stored as a string of 1s and 0s. In a quantum system, quantum bits, or “qubits” are stored in a so-called “superposition state” in which they can be both 1s and 0 at the same time. This enables them to perform lots of calculations at the same time. Quantum computers probably won’t be the ideal solution for all types of computation, but they should be much faster than classical computers for many.
The researchers encoded information into the nuclei of phosphorus atoms held in a sliver of purified silicon at -269C – the lowest temperature possible. Magnetic field pulses were used to tilt the spin of the nuclei and create superposition states. When they raised the system to room temperature (just above 25C) the superposition states survived for 39 minutes. The team was able to carry on manipulating the qubits as they cooled the sample back down to near absolute zero. At cryogenic temperatures, their quantum memory system remained coherent for three hours.
Some major hurdles remain before large-scale quantum computations can be performed at room temperature. For one thing, the spins of the 10 billion or so phosphorus ions used in this experiment were all placed in the same quantum state, whereas to run calculations, the different qubits will need to be in different states.
For another, their memory device was built with a highly purified form of silicon – free from the magnetic isotopes which interfere with the spin of nuclei. Nevertheless, the fact that silicon was the material used is significant. The massive investment in computing with silicon means it has a lot of potential for engineering.
