Coherence Properties of Transmon Qudits

Janos Adam

Quantum computing is conventionally performed on qubits, but many platforms have access to higher energy levels which open up the possibility to use excited states for quantum computation. Higher level qubits – or qudits – have many benefits: they offer a larger state space, can reduce complexity of quantum circuits or can improve readout fidelity. Despite these benefits, qudits face several drawbacks; one of them is shorter coherence times: faster relaxation restricts the available time for computing.
In this poster I show my efforts to characterize the relaxation properties of qudits – for this I ran experiments on the IBM transmon system. The attached figure shows the population dynamics of a qutrit. The time it takes for |2> to relax into |1> is half of the time it takes it to relax from |1> to |0>. This shows that higher levels decohere faster – as expected. However, the relaxation is still long enough which makes the transmon to be a good candidate for qudits.

Funding Sources: N/A