Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing the coherence of solid-state qubits at avoided crossings   Optically addressable paramagnetic defects in wide-band-gap semiconductors
are promising platforms for quantum communications and sensing. The presence of
avoided crossings between the electronic levels of these defects can
substantially alter their quantum dynamics and be both detrimental and
beneficial for quantum information applications. Avoided crossings give rise to
clock transitions, which can significantly improve protection from magnetic
noise and favorably increase coherence time. However, the reduced coupling
between electronic and nuclear spins at an avoided crossing may be detrimental
to applications where nuclear spins act as quantum memories. Here we present a
combined theoretical and experimental study of the quantum dynamics of
paramagnetic defects interacting with a nuclear spin bath at avoided crossings.
We develop a computational approach based on a generalization of the cluster
expansion technique, which can account for processes beyond pure dephasing and
describe the dynamics of any solid-state spin-qubits near avoided crossings.
Using this approach and experimental validation, we determine the change in
nature and source of noise at avoided crossings for divacancies in SiC. We find
that we can condition the clock transition of the divacancies in SiC on
multiple adjacent nuclear spins states. In our experiments, we demonstrate that
one can suppress the effects of fluctuating charge impurities with depletion
techniques, leading to an increased coherence time at clock transition, limited
purely by magnetic noise. Combined with ab-initio predictions of spin
Hamiltonian parameters, the proposed theoretical approach paves the way to
designing the coherence properties of spin qubits from first principles.

10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
15
The categories of this paper are: nucl-ex