TY  - JOUR
ID  - discovery1474850
N2  - Whether a quantum bath can be approximated as classical Gaussian noise is a fundamental issue in central spin decoherence and also of practical importance in designing noise-resilient quantum control. Spin qubits based on bismuth donors in silicon have tunable interactions with nuclear spin baths and are first-order insensitive to magnetic noise at so-called clock transitions (CTs). This system is therefore ideal for studying the quantum/classical Gaussian nature of nuclear spin baths since the qubit-bath interaction strength determines the back-action on the baths and hence the adequacy of a Gaussian noise model. We develop a Gaussian noise model with noise correlations determined by quantum calculations and compare the classical noise approximation to the full quantum bath theory. We experimentally test our model through a dynamical decoupling sequence of up to 128 pulses, finding good agreement with simulations and measuring electron spin coherence times approaching 1 s?notably using natural silicon. Our theoretical and experimental study demonstrates that the noise from a nuclear spin bath is analogous to classical Gaussian noise if the back-action of the qubit on the bath is small compared to the internal bath dynamics, as is the case close to CTs. However, far from the CTs, the back-action of the central spin on the bath is such that the quantum model is required to accurately model spin decoherence.
SN  - 1098-0121
UR  - http://dx.doi.org/10.1103/PhysRevB.92.161403
JF  - PHYSICAL REVIEW B
A1  - Ma, W-L
A1  - Wolfowicz, G
A1  - Li, S-S
A1  - Morton, JJL
A1  - Liu, R-B
TI  - Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon
AV  - public
VL  - 92
Y1  - 2015/10/08/
N1  - ©2015 American Physical Society
ER  -