Maximizing the purity of a qubit evolving in an anisotropic environment

Abstract

We provide a general method to calculate and maximize the purity of a qubit interacting with an anisotropic non-Markovian environment. Counter to intuition, we find that the purity is often maximized by preparing and storing the qubit in a superposition of non-interacting eigenstates. For a model relevant to decoherence of a heavy-hole spin qubit in a quantum dot or for a singlet-triplet qubit for two electrons in a double quantum dot, we show that preparation of the qubit in its non-interacting ground state can actually be the worst choice to maximize purity. We further give analytical results for spin-echo envelope modulations of arbitrary spin components of a hole spin in a quantum dot, going beyond a standard secular approximation. We account for general dynamics in the presence of a pure-dephasing process and identify a crossover timescale at which it is again advantageous to initialize the qubit in the non-interacting ground state. Finally, we consider a general two-axis dynamical decoupling sequence and determine initial conditions that maximize purity, minimizing leakage to the environment.

v1: 15 pages, 9 figures; v2: 19 pages, 14 figures, new sections on Born-Markov limit and dynamical decoupling

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Cited by in corpus (5)

• Recent advances in hole-spin qubits
• First-principles hyperfine tensors for electrons and holes in GaAs and silicon
• Gate-Tunable Spin-Orbit Coupling in a Germanium Hole Double Quantum Dot
• Filter function formalism beyond pure dephasing and non-Markovian noise in singlet-triplet qubits
• Hole-Spin-Echo Envelope Modulations