Exponential decay in a spin bath

Coish, W. A.; Fischer, Jan; Loss, Daniel

doi:10.1103/physrevb.77.125329

Cited by 80 publications

(169 citation statements)

References 46 publications

(54 reference statements)

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“…These short operation times together with the demonstrated coherence times of a few microseconds 7 and predicted coherence times of up to 100 microseconds [27][28][29] suggest that the requirements for quantum error correction of two-electron spin qubits are within reach. Furthermore, our ability to record the magnetic field gradient opens the way towards feedback control of the nuclear environment that would prolong T * 2 and thereby reduce the number of error correcting pulses needed.…”

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confidence: 99%

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

et al. 2009

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Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

et al. 2009

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“…Usually, interactions between a single electron spin and many weakly interacting spins (as described by the "central spin problem" 19 ) can lead to complicated evolution of the joint quantum system [20][21][22][23][24][25][26][27][28][29][30][31] . Moreover, the nuclear spin bath may maintain coherence over a long time, which may in general result in coherent back-action on the electron spin.…”

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Semiclassical model for the dephasing of a two-electron spin qubit coupled to a coherently evolving nuclear spin bath

et al. 2011

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The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters We study electron spin decoherence in a two-electron double quantum dot due to the hyperfine interaction, under spin-echo conditions as studied in recent experiments. We develop a semi-classical model for the interaction between the electron and nuclear spins, in which the time-dependent Overhauser fields induced by the nuclear spins are treated as classical vector variables. Comparison of the model with experimentally-obtained echo signals allows us to quantify the contributions of various processes such as coherent Larmor precession and spin diffusion to the nuclear spin evolution.

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“…To further advance spin-based quantum computing, it is vital to mitigate decoherence due to the interaction of the electron spin with the spins of nuclei of the host material. Understanding the dynamics of this system is also of great fundamental interest 11,12 .Through the hyperfine interaction, an electron spin in a GaAs quantum dot is subjected to an effective magnetic field produced by the nuclear spins. Under typical experimental conditions, this so-called 'Overhauser field' has a random magnitude and direction.…”

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Dephasing time of GaAs electron-spin qubits coupled to a nuclear bath exceeding 200 μs

et al. 2010

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Qubits, the quantum mechanical bits required for quantum computing, must retain their quantum states for times long enough to allow the information contained in them to be processed. In many types of electron-spin qubits, the primary source of information loss is decoherence due to the interaction with nuclear spins of the host lattice. For electrons in gate-defined GaAs quantum dots, spin-echo measurements have revealed coherence times of about 1 µs at magnetic fields below 100 mT (refs 1,2). Here, we show that coherence in such devices can survive much longer, and provide a detailed understanding of the measured nuclearspin-induced decoherence. At fields above a few hundred millitesla, the coherence time measured using a singlepulse spin echo is 30 µs. At lower fields, the echo first collapses, but then revives at times determined by the relative Larmor precession of different nuclear species. This behaviour was recently predicted 3,4 , and can, as we show, be quantitatively accounted for by a semiclassical model for the dynamics of electron and nuclear spins. Using a multiple-pulse Carr-Purcell-Meiboom-Gill echo sequence, the decoherence time can be extended to more than 200 µs, an improvement by two orders of magnitude compared with previous measurements 1,2,5 .The promise of quantum-dot spin qubits as a solid-state approach to quantum computing is demonstrated by the successful realization of initialization, control and single-shot readout of electron-spin qubits in GaAs quantum dots using optical 6 , magnetic 7 and fully electrical 8-10 techniques. To further advance spin-based quantum computing, it is vital to mitigate decoherence due to the interaction of the electron spin with the spins of nuclei of the host material. Understanding the dynamics of this system is also of great fundamental interest 11,12 .Through the hyperfine interaction, an electron spin in a GaAs quantum dot is subjected to an effective magnetic field produced by the nuclear spins. Under typical experimental conditions, this so-called 'Overhauser field' has a random magnitude and direction. Typically, measurements of the coherent electron-spin precession involve averaging over many experimental runs, and thus over many Overhauser field configurations. As a result, the coherence signal is suppressed for evolution times τ ∼ > T 2 * ≈ 10 ns (refs 1, 2). However, the nuclear spins evolve much more slowly than the electron spins, so that the Overhauser field is nearly static over sufficiently short time intervals. Therefore, one can partially eliminate the effect of the random nuclear field by flipping the electron spin halfway through an interval of free precession, a procedure known as Hahn echo. The random contributions of the Overhauser field to the electron-spin precession before and after the spin reversal then approximately cancel out. For longer evolution times, the effective field acting on the electron spin generally changes over the precession interval. This change leads to an eventual loss of coherence on a timescale determined ...

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Exponential decay in a spin bath

Cited by 80 publications

References 46 publications

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

Semiclassical model for the dephasing of a two-electron spin qubit coupled to a coherently evolving nuclear spin bath

Dephasing time of GaAs electron-spin qubits coupled to a nuclear bath exceeding 200 μs

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