Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single-shot readout and relaxation of singlet/triplet states in
  exchange-coupled $^{31}$P electron spins in silicon   We present the experimental observation of a large exchange coupling $J
\approx 300$ $\mu$eV between two $^{31}$P electron spin qubits in silicon. The
singlet and triplet states of the coupled spins are monitored in real time by a
Single-Electron Transistor, which detects ionization from tunnel-rate-dependent
processes in the coupled spin system, yielding single-shot readout fidelities
above 95%. The triplet to singlet relaxation time $T_1 \approx 4$ ms at zero
magnetic field agrees with the theoretical prediction for $J$-coupled $^{31}$P
dimers in silicon. The time evolution of the 2-electron state populations gives
further insight into the valley-orbit eigenstates of the donor dimer, valley
selection rules and relaxation rates, and the role of hyperfine interactions.
These results pave the way to the realization of 2-qubit quantum logic gates
with spins in silicon, and highlight the necessity to adopt gating schemes
compatible with weak $J$-coupling strengths.

27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an