Qubits are the building blocks of a quantum processor, and they get their name from the fact that they recount a series of complex superpositions of two fundamental quantum states. The ability of qubits to encode significantly more databases than a traditional bit — an infinite set of states between zero and one — contributes to its power. Quantum gates that manipulate the state of individual qubits are called unitary operators in mathematics.

The transmon concept describes Rigetti's superconducting quantum processors. Each physical qubit is an anharmonic oscillator, which implies that as the qubit progresses up the assert ladder, the power differences between subsequent qubit power states decrease.

Why not aim for even higher levels? In practice, as you ascend higher and higher up the transmon, the dephasing rate of superconducting qudits grows substantially. The coherence duration of the merely second excited state (|2>), on the other hand, can be on the order of many microseconds, allowing for practical computations.

Quil-T, a pulse-level extension to Quil, now gives Rigetti experimental access to qutrit operations. Users will gain access to a new set of gates between the first and second states of the qutrit for most devices, in addition to the regular suite of qubit calibrations.