Fig. 1
From: Achieving the Heisenberg limit in quantum metrology using quantum error correction
Metrology schemes and qubit probe. a The sequential scheme. One probe sequentially senses the parameter for time t, with quantum controls applied every dt. b The parallel scheme. N probes sense the parameter for time t/N in parallel. The parallel scheme can be simulated by the sequential scheme. c The relation between the signal Hamiltonian, the noise, and the QEC code on the Bloch sphere for a qubit probe
