We advance spin noise spectroscopy to the ultimate limit of single spin detection. This technique enables the measurement of the spin dynamic of a single heavy hole localized in a flat (InGa)As quantum dot. Magnetic field and light intensity dependent studies reveal even at low magnetic fields a strong magnetic field dependence of the longitudinal heavy hole spin relaxation time with an extremely long T 1 of ≥ 180 μs at 31 mT and 5 K. The wavelength dependence of the spin noise power discloses for finite light intensities an inhomogeneous single quantum dot spin noise spectrum which is explained by charge fluctuations in the direct neighborhood of the quantum dot. The charge fluctuations are corroborated by the distinct intensity dependence of the effective spin relaxation rate. DOI: 10.1103/PhysRevLett.112.156601 PACS numbers: 72.25.Rb, 72.70.+m, 78.67.Hc, 85.75.-d Optical spin noise spectroscopy (SNS) is in principle a nondestructive measurement technique which has been transferred from quantum optics to semiconductor physics in 2005 [1]. The technique exploits the ever present random fluctuations of spin polarization at thermal equilibrium which are detected by optical Faraday rotation and contain according to the fluctuation dissipation theorem the full dynamic of the spin system. Spin noise spectroscopy is potentially suited to study prospective quantum information systems like quantum repeaters, where photon imparted spin entanglement plays a crucial role [2], or semiconductor spin systems, where optical excitation demolishes the intrinsic spin dynamic, e.g., by carrier heating, creation of free carriers, or electron hole spin relaxation via the Bir-Aronov-Pikus mechanism [3,4]. The first SNS measurements in semiconductors were demonstrated on bulk GaAs where about 10 billion electrons contributed to the spin noise (SN) signal [1]. Three years later, SNS revealed the intrinsic spin lifetime of electrons in (110) quantum wells at an ensemble of about 170,000 electrons [5]. In 2012, two experiments demonstrated SNS on quantum dot (QD) ensembles where the signal resulted from as low as 50 heavy holes [6,7]. In this publication we push SNS to the ultimate limit and use the technique to study the fragile spin relaxation dynamic of a single heavy hole localized in a single (InGa)As quantum dot. Thus, SNS finds its way into the very active field of optical single spin detection in quantum dots which has been extremely successful, e.g., studying electron and transverse hole spin dynamic and coherent spin control [8][9][10].During the last few years, strongly localized heavy holes in single (InGa)As quantum dots have attracted considerable attention as a new candidate for semiconductor quantum information qubits [11][12][13][14][15]. Theory and experiment show that such heavy holes have in comparison to electrons a significantly longer inhomogeneous transverse spin dephasing time T Ã 2 since their p-type wave function with vanishing probability density at the nuclei leads to a rather weak, Ising-like hyperfine ...

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.This article gives an overview on the advance of spin noise spectroscopy (SNS) in semiconductors in the past 8 years from the first measurements in bulk n-GaAs [Oestreich et al., Phys. Rev. Lett. 95, 216603 (2005)] up to the recent achievement of optical detection of the intrinsic spin fluctuations of a single hole confined in an individual self-assembled quantum dot [Dahbashi et al., arXiv:1306.3183 (2013]. We discuss the general technical implementation of optical SNS and the invaluable profit of the introduction of real-time fast Fourier transform analysis into the data acquisition. By now, the full spin dynamic from the milli-to picosecond timescales can be addressed by SNS and the technique quickly strides ahead to enable real quantum non-demolition measurements in semiconductors.Spin noise spectra recorded in 2005 in bulk n-GaAs with approximately 10 9 electron spins (Oestreich et al.) and 2013 (Dahbashi et al.) for a single hole spin. The integration time for the latter is more than a factor of 40 shorter due to the significant advances in the measurement technique.

We measure the spin dephasing of holes localized in self-assembled (InGa)As quantum dots by spin noise spectroscopy. The localized holes show a distinct hyperfine interaction with the nuclear spin bath despite the p-type symmetry of the valence band states. The experiments reveal a short spin relaxation time {\tau}_{fast}^{hh} of 27 ns and a second, long spin relaxation time {\tau}_{slow}^{hh} which exceeds the latter by more than one order of magnitude. The two times are attributed to heavy hole spins aligned perpendicular and parallel to the stochastic nuclear magnetic field. Intensity dependent measurements and numerical simulations reveal that the long relaxation time is still obscured by light absorption, despite low laser intensity and large detuning. Off-resonant light absorption causes a suppression of the spin noise signal due to the creation of a second hole entailing a vanishing hole spin polarization.Comment: accepted to be published in AP

We present spin-noise spectroscopy measurements on an ensemble of donor-bound electrons in ultrapure GaAs:Si covering temporal dynamics over 6 orders of magnitude from milliseconds to nanoseconds. The spin-noise spectra detected at the donor-bound exciton transition show the multifaceted dynamical regime of the ubiquitous mutual electron and nuclear spin interaction typical for III-V-based semiconductor systems. The experiment distinctly reveals the finite Overhauser shift of an electron spin precession at zero external magnetic field and a second contribution around zero frequency stemming from the electron spin components parallel to the nuclear spin fluctuations. Moreover, at very low frequencies, features related with time-dependent nuclear spin fluctuations are clearly resolved making it possible to study the intricate nuclear spin dynamics at zero and low magnetic fields. The findings are in agreement with the developed model of electron and nuclear spin noise. DOI: 10.1103/PhysRevLett.115.176601 PACS numbers: 72.25.Rb, 72.70.+m, 78.47.db, 85.75.-d Harnessing coherence is one of the central topics in current research and attracts high interest due to the complex fundamental physics bridging quantum mechanics and statistics as well as due to prospective applications for information processing [1][2][3]. The solid state quantum states based upon the spin degree of freedom of confined carriers in semiconductors are at the forefront of many current research activities in this field. In this respect, optically addressable electron and hole spin quantum states in III-V-based semiconductor systems bear the beauty of efficient options for initialization, manipulation, and readout by light in combination with exceptional sample quality [4]. Currently, a promising system for these tasks are donorbound electrons in ultrahigh quality, very weakly n-doped GaAs since the widely spaced, quasi-isolated electrons act as an ensemble of identical, individually localized atoms [5,6]. However, the ostensible catch of this approach is the inherent interaction with the nuclear spin bath which has been addressed in many different systems so far [7][8][9][10][11].In principle, there are different approaches to deal with the decoherence imposed via the hyperfine interaction. On the first sight, the most obvious way is to replace the isotopes carrying a nuclear spin with spinless isotopes like in 28 Si [12] but silicon has the drawback of an indirect gap. Direct semiconductors with spinless isotopes like, e.g., isotopically purified II-VI systems have yet the drawback of inferior sample quality. In single III-V-based quantum dots, the hyperfine interaction can be reduced by either moving on to hole spins which show a diminished hyperfine interaction [13][14][15] or by polarizing the nuclei in order to make them less effective [16,17]. Besides that, the mutual interaction between carrier and nuclear spins is also strain dependent and strongly varying coupling strengths in such nanostructures result in a row of widely discussed pr...

This corrects the article DOI: 10.1103/PhysRevLett.111.186602.