On fault tolerant single-shot logical state preparation and robust long-range entanglement

Understand

Preparing encoded logical states is the first step in a fault-tolerant quantum computation.

• Standard approaches based on concatenation or repeated measurement incur a significant time overhead.
• The Raussendorf-Bravyi-Harrington cluster state offers an alternative: a single-shot preparation of encoded states of the surface code, by means of a constant depth quantum circuit, followed by a single round of measurement and classical feedforward.
• In this work we generalize this approach and prove that single-shot logical state preparation can be achieved for arbitrary quantum LDPC codes.