Magic State Cultivation | Quantum Colloquium

Historically, making magic states was expected to be the dominant cost of fault tolerant quantum computation. This talk will discuss a construction, called "magic state cultivation", that (building on many previous results) seriously questions this dominance. Cultivation efficiently prepares good T states, fits inside a surface code patch, only uses square grid connectivity, and uses roughly the same number of physical gates as a lattice surgery CNOT gate of equivalent reliability. Compared to prior work, cultivation uses an order of magnitude fewer qubit-rounds to reach infidelities in the billionths while subjected to 0.1% uniform depolarizing circuit noise. Cultivation is extremely sensitive to changes in the noise: halving the circuit noise strength would improve the achievable logical error rate by a factor of 30 while reducing the cost by a factor of 10. Cultivation's efficiency and strong response to improvements in noise suggest that further magic state distillation may never be needed in practice.