MEMO to the developers of superfast quantum computers: eschew the binary systems used in conventional computers. By switching to a five-state system, you will find it easier to build the staggeringly powerful machines. So claim Matthew Neeley and his team at the University of California, Santa Barbara (UCSB).
The development of quantum computers has so far followed the traditional binary computing model, using quantum bits 鈥� qubits 鈥� in which two states can be encoded in the form of the quantum spin angle in atoms, electrons or photons. It is the ability of such particles to exist in multiple quantum states at once that should one day enable quantum computers to perform vast numbers of calculations simultaneously.
Neeley鈥檚 team has demonstrated it is possible to take that further and operate a five-state quantum system, using a superconducting aluminium and silicon circuit on a sapphire wafer that, at 0.025 kelvin, acts like an 鈥渁rtificial atom鈥�. The five-state unit (pictured) is known as a 鈥渜udit鈥�.
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鈥淭here鈥檚 more information stored in a qudit than a qubit, so a given computation can be done with fewer qudits,鈥� Neeley told New 杏吧原创.
By firing microwave photons of five different frequencies into the circuit, they were able to make it to jump between five discrete energy levels. 鈥淲e also developed a quantum measuring technique that can distinguish between all of these levels,鈥� says Neeley.
鈥淭he team was able to make an 鈥榓rtificial atom鈥� jump between five discrete energy levels鈥�
Because, in probabilistic terms, the circuit鈥檚 five quantum states are able to exist simultaneously, the team had a working qudit on their hands (Science, ).
One qudit alone is of little use, however. Jonathan Home at the US National Institute of Standards and Technology in Boulder, Colorado, says Neeley鈥檚 team needs to extend its basic system in such a way that two or more qudits can transport information between them, which would allow more complex computational operations to be undertaken.
鈥淒esigning the sort of system where two qudits interact, but still retain the interesting properties of a five-level system, will be a major challenge,鈥� Home says.
