The supercharged Qubit: researchers present the Qutrit


Rigetti Computing, one of the players in the field of quantum computing, has announced a new development which is sure to surprise at least some of its competitors. While typical quantum scaling techniques have focused on either improving error correction or increasing the number of qubits, the new concept allows qubits to increase their utility by unlocking a third state, instead of the usual two. Qutrits, as the company calls it, have entered the fray of quantum computing.

Typical qubits perform calculations on two possible quantum states. This duality meant that qubit states were previously described (in practical applications) in terms of their “ground state” (g), corresponding to “0”; and their “excited state” (e), corresponding to “1”. Qubits do work through the endless subdivisions between these two states. Qutrits, however, unlock a third quantum state “above 1” – and yes, the state is described as “2”.

Qubit states diagram

Qutrits (shown at right) improve performance by reaching higher states than qubits (left). (Image credit: Informatique Rigetti)

This essentially means that qutrits contain more information than qubits – the equivalent of the endless encoding possibilities between 0 and 2, instead of between 0 and 1. This allows them to handle even larger workloads. . In cases where pure acceleration isn’t the goal, however, Rigetti says his qutrits may also unlock new error correction techniques, another of the current bottlenecks between quantum computing and sound. adoption by the mainstream market.

Of course, quantum computing is a fickle mistress and tends to break out of its stable state, leading to quantum decoherence and its consequences. These range from no work at all to severe limitations in the quality, and therefore usability, of the calculation results produced. Naturally, bringing the qubits beyond their state e greatly decreases the longevity of the coherence of the system. This is part of the reason why Rigetti says his outputs can only do useful work at a scale of “several microseconds”.

This is still more than enough to perform useful calculations – much like our classic PCs that run billions of cycles per second, it’s just at a much larger scale of computation. Qubits can theoretically reach states greater than “2”, but as expected, the stability drops so much that no usable work can (at least currently) be done on those states, locking that particular gate for now.

Rigetti Computing has already made its qutrit systems available (on an experimental basis) to researchers and customers through its Quil-T instruction set architecture for quantum computing. It is yet another flag in the race for quantum computing. Now it will be necessary to see if other companies are ready to rally to this.


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