Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Realizing singlet-triplet qubits in multivalley Si quantum dots   There has been significant progress in the implementation and manipulation of
singlet-triplet qubits in GaAs quantum dots. Given the considerably longer spin
coherence times measured in Si, considerable interest has been generated
recently in Si quantum dots. The physics of these systems is considerably more
complex than the physics of GaAs quantum dots owing to the presence of the
valley degree of freedom, which constitutes the focus of this work. In this
paper we investigate the physics of Si quantum dots and focus on the
feasibility of quantum coherent singlet-triplet qubit experiments analogous to
those performed in GaAs. This additional degree of freedom greatly increases
the complexity of the ground state and gives rise to highly nontrivial and
interesting physics in the processes of qubit initialization, coherent
manipulation and readout. We discuss the operational definition of a qubit in
Si-based quantum dots. We find that in the presence of valley degeneracy a
singlet-triplet qubit cannot be constructed, whereas for large valley splitting
(>>k_B*T) the experiment is similar to GaAs. We show that experiments on
singlet-triplet qubits analogous to those in GaAs would provide a method for
estimating the valley coupling in Si. A Zeeman field distinguishes between
different initialized states for any valley splitting and provides a tool to
determine the size of this splitting.

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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
9
The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: stat
1
The categories of this paper are: cs
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The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an