Physical error floors of qubit hardware platforms

4 problems

• Can radiation-induced error bursts in superconducting chips be made rare enough?

  Partially resolved

  Superconducting quantum chips sometimes suffer sudden bursts of errors that hit many qubits together, caused by cosmic rays and natural radioactivity breaking superconducting electron pairs. Whether chip design can make such bursts rare enough that they almost never overwhelm an error-correcting code is not settled.

• Microscopic origin of anomalous motional heating in ion traps

  Open

  Ions held above metal electrodes heat up far faster than the electrical noise of the metal predicts, which spoils the shared motion that ion-qubit gates use. Which surface process produces this excess electric-field noise is not established.

• Maximum photon loss tolerable in linear-optical fault-tolerant architectures

  Open

  Photonic quantum computers lose photons in sources, chips and detectors, and their two-photon operations succeed only part of the time. The largest loss rate at which error correction can still work is not known.

• Intrinsic error floor of Rydberg-blockade entangling gates

  Open

  Neutral-atom computers entangle two atoms by briefly lifting them to giant, strongly interacting Rydberg states (highly excited atomic states), which decay and are disturbed by room-temperature heat radiation. How small the gate error can be made, given these limits, is not known.