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Initialization of Neutral and Charged Exciton Spin States in a Telecom-Emitting Quantum Dot
Authors:
Giora Peniakov,
Johannes Michl,
Mohamed Helal,
Raphael Joos,
Michael Jetter,
Simone L. Portalupi,
Peter Michler,
Sven Höfling,
Tobias Huber-Loyola
Abstract:
Photonic cluster states are highly entangled states that allow for photonic quantum computing and memory-less quantum repeaters. Their generation has been recently demonstrated using semiconductor quantum dots emitting at the 900 nm wavelength range. However, a similar demonstration at the communication-optimal telecom range has remained elusive. A key ingredient that is still missing is an approp…
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Photonic cluster states are highly entangled states that allow for photonic quantum computing and memory-less quantum repeaters. Their generation has been recently demonstrated using semiconductor quantum dots emitting at the 900 nm wavelength range. However, a similar demonstration at the communication-optimal telecom range has remained elusive. A key ingredient that is still missing is an appropriate optical excitation method. A central requirement of such a method is to allow an arbitrary spin initialization of quantum dot excitonic complexes. In this work, we report on developing such a method based on a quasi-resonant p-shell excitation for a telecom-C-band-emitting quantum dot. We show qubit writing of a neutral exciton and spin-preserving excitation of a negative trion. Using the Larmor precession of the negative trion under an externally applied magnetic field, we determine the in-plane g-factors of both the electron and the hole in the investigated quantum dot. In addition, we measure a lower bound on the hole coherence time, $T_{2}^{*}>6.4$ ns, boosting its candidacy as a sound photon entangler for more advanced quantum photonic schemes.
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Submitted 29 April, 2025;
originally announced April 2025.
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Two-Photon Interference from an InAs Quantum Dot emitting in the Telecom C-Band
Authors:
Jaewon Kim,
Jochen Kaupp,
Yorick Reum,
Giora Peniakov,
Johannes Michl,
Felix Kohr,
Monika Emmerling,
Martin Kamp,
Yong-Hoon Cho,
Tobias Huber-Loyola,
Sven Höfling,
Andreas T. Pfenning
Abstract:
Two-photon interference from an InAs/InAlGaAs quantum dot (QD) emitting in the telecom C-band with a raw two-photon interference visibility of $V_{HOM}=(71.9\pm0.2)$ % is demonstrated. This is achieved by a two-fold approach: an improvement of the molecular beam epitaxial growth for better QDs, and integration of the QDs into an optical circular Bragg grating resonator for a Purcell enhancement of…
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Two-photon interference from an InAs/InAlGaAs quantum dot (QD) emitting in the telecom C-band with a raw two-photon interference visibility of $V_{HOM}=(71.9\pm0.2)$ % is demonstrated. This is achieved by a two-fold approach: an improvement of the molecular beam epitaxial growth for better QDs, and integration of the QDs into an optical circular Bragg grating resonator for a Purcell enhancement of the radiative decay rate. The quantum optical properties of the fabricated device are studied by means of time-correlated single-photon counting under quasi-resonant excitation of the charged exciton line. A reduced lifetime of $T_1=(257.5\pm0.2)$ ps is found corresponding to a Purcell factor of $F_P\geqq(4.7\pm0.5)$. Pronounced anti-bunching of the second-order autocorrelation function at zero time delay $g^{(2)} (0)=(0.0307\pm0.0004)$ confirms the single-photon emission character. The two-photon interference is demonstrated with an unbalanced Mach-Zehnder interferometer in Hong-Ou-Mandel configuration. We discuss strategies how to further improve the indistinguishability, and provide a survey of the state-of-the art.
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Submitted 11 August, 2025; v1 submitted 27 January, 2025;
originally announced January 2025.
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Purcell-Enhanced Single-Photon Emission in the Telecom C-Band
Authors:
Jochen Kaupp,
Yorick Reum,
Felix Kohr,
Johannes Michl,
Quirin Buchinger,
Adriana Wolf,
Giora Peniakov,
Tobias Huber-Loyola,
Andreas Pfenning,
Sven Höfling
Abstract:
Purcell-enhanced quantum dot single-photon emission in the telecom C-band from InAs quantum dots inside circular Bragg grating cavities is shown. The InAs quantum dots are grown by means of molecular beam epitaxy on an InP substrate and are embedded into a quaternary $\mathrm{In}_{0.53}\mathrm{Al}_{0.23}\mathrm{Ga}_{0.24}\mathrm{As}$ membrane structure. In a post-growth flip-chip process with subs…
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Purcell-enhanced quantum dot single-photon emission in the telecom C-band from InAs quantum dots inside circular Bragg grating cavities is shown. The InAs quantum dots are grown by means of molecular beam epitaxy on an InP substrate and are embedded into a quaternary $\mathrm{In}_{0.53}\mathrm{Al}_{0.23}\mathrm{Ga}_{0.24}\mathrm{As}$ membrane structure. In a post-growth flip-chip process with subsequent substrate removal and electron beam-lithography, circular Bragg grating ("bullseye") resonators are defined. Micro-photoluminescence studies of the devices at cryogenic temperatures of T = 5 K reveal individual quantum dot emission lines into a pronounced cavity mode. Time-correlated single-photon counting measurements under above-band gap excitation yield Purcell-enhanced excitonic decay times of $τ= (180 \pm 3)$ ps corresponding to a Purcell factor of $F_P = (6.7 \pm 0.6)$. Pronounced photon antibunching with a background limited $g^{(2)}(0) = (0.057 \pm 0.004)$ is observed, which demonstrates that the light originated mostly from one single quantum dot.
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Submitted 3 November, 2023;
originally announced November 2023.
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Strain-free GaSb quantum dots as single-photon sources in the telecom S-band
Authors:
Johannes Michl,
Giora Peniakov,
Andreas Pfenning,
Joonas Hilska,
Abhiroop Chellu,
Andreas Bader,
Mircea Guina,
Sven Höfling,
Teemu Hakkarainen,
Tobias Huber-Loyola
Abstract:
Creating single photons in the telecommunication wavelength range from semiconductor quantum dots (QDs) and interfacing them with spins of electrons or holes has been of high interest in recent years, with research mainly focusing on indium based QDs. However, there is not much data on the optical and spin properties of galliumantimonide (GaSb) QDs, despite it being a physically rich system with a…
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Creating single photons in the telecommunication wavelength range from semiconductor quantum dots (QDs) and interfacing them with spins of electrons or holes has been of high interest in recent years, with research mainly focusing on indium based QDs. However, there is not much data on the optical and spin properties of galliumantimonide (GaSb) QDs, despite it being a physically rich system with an indirect to direct bandgap crossover in the telecom wavelength range. Here, we investigate the (quantum-) optical properties of GaSb quantum dots, which are fabricated by filling droplet-etched nanoholes in an aluminum-galliumantimonide (AlGaSb) matrix. We observe photoluminescence (PL) features from isolated and highly symmetric QDs that exhibit narrow linewidth in the telecom S-band and show an excitonic fine structure splitting of $ΔE=(12.0\pm0.5)μeV$. Moreover, we perform time-resolved measurements of the decay characteristics of an exciton and measure the second-order photon autocorrelation function of the charge complex to $g^{(2)}(0)=0.16\pm0.02$, revealing clear antibunching and thus proving the capability of this material platform to generate non-classical light.
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Submitted 7 May, 2023;
originally announced May 2023.
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Confined-state physics and signs of fermionization of moiré excitons in WSe$_2$/MoSe$_2$ heterobilayers
Authors:
Frederik Lohof,
Johannes Michl,
Alexander Steinhoff,
Bo Han,
Martin von Helversen,
Sefaattin Tongay,
Kenji Watanabe,
Takashi Taniguchi,
Sven Höfling,
Stephan Reitzenstein,
Carlos Anton-Solanas,
Christopher Gies,
Christian Schneider
Abstract:
We revisit and extend the standard bosonic interpretation of interlayer excitons in the moiré potential of twisted heterostructures of transition-metal dichalcogenides. In our experiments, we probe a high quality MoSe$_2$/WSe$_2$ van der Waals bilayer heterostructure via density-dependent photoluminescence spectroscopy and reveal strongly developed, unconventional spectral shifts of the emergent m…
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We revisit and extend the standard bosonic interpretation of interlayer excitons in the moiré potential of twisted heterostructures of transition-metal dichalcogenides. In our experiments, we probe a high quality MoSe$_2$/WSe$_2$ van der Waals bilayer heterostructure via density-dependent photoluminescence spectroscopy and reveal strongly developed, unconventional spectral shifts of the emergent moiré exciton resonances. The observation of saturating blueshifts of successive exciton resonances allow us to explain their physics in terms of a model utilizing fermionic saturable absorbers. This approach is strongly inspired by established quantum-dot models, which underlines the close analogy of interlayer excitons trapped in pockets of the moiré potential, and quantum emitters with discrete eigenstates.
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Submitted 15 May, 2023; v1 submitted 28 February, 2023;
originally announced February 2023.
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Physics-Based and Closed-Form Model for Cryo-CMOS Subthreshold Swing
Authors:
Arnout Beckers,
Jakob Michl,
Alexander Grill,
Ben Kaczer,
Marie Garcia Bardon,
Bertrand Parvais,
Bogdan Govoreanu,
Kristiaan De Greve,
Gaspard Hiblot,
Geert Hellings
Abstract:
Cryogenic semiconductor device models are essential in designing control systems for quantum devices and in benchmarking the benefits of cryogenic cooling for high-performance computing. In particular, the saturation of subthreshold swing due to band tails is an important phenomenon to include in low-temperature analytical MOSFET models as it predicts theoretical lower bounds on the leakage power…
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Cryogenic semiconductor device models are essential in designing control systems for quantum devices and in benchmarking the benefits of cryogenic cooling for high-performance computing. In particular, the saturation of subthreshold swing due to band tails is an important phenomenon to include in low-temperature analytical MOSFET models as it predicts theoretical lower bounds on the leakage power and supply voltage in tailored cryogenic CMOS technologies with tuned threshold voltages. Previous physics-based modeling required to evaluate functions with no closed-form solutions, defeating the purpose of fast and efficient model evaluation. Thus far, only the empirically proposed expressions are in closed form. This article bridges this gap by deriving a physics-based and closed-form model for the full saturating trend of the subthreshold swing from room down to low temperature. The proposed model is compared against experimental data taken on some long and short devices from a commercial 28-nm bulk CMOS technology down to 4.2 K.
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Submitted 24 September, 2023; v1 submitted 22 December, 2022;
originally announced December 2022.
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Intrinsic circularly-polarized exciton emission in a twisted van-der-Waals heterostructure
Authors:
J. Michl,
S. A. Tarasenko,
F. Lohof,
G. Gies,
M. von Helversen,
R. Sailus,
S. Tongay,
T. Taniguchi,
K. Watanabe,
T. Heindel,
S. Reitzenstein,
T. Shubina,
S. Höfling,
C. Antón-Solanas,
C. Schneider
Abstract:
The investigation of excitons in van-der-Waals heterostructures has led to profound insights into the interplay of crystal symmetries and fundamental effects of light-matter coupling. In particular, the polarization selection rules in undistorted, slightly twisted heterostructures of MoSe$_2$/WSe$_2$ were found to be connected with the Moiré superlattice. Here, we report the emergence of a signifi…
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The investigation of excitons in van-der-Waals heterostructures has led to profound insights into the interplay of crystal symmetries and fundamental effects of light-matter coupling. In particular, the polarization selection rules in undistorted, slightly twisted heterostructures of MoSe$_2$/WSe$_2$ were found to be connected with the Moiré superlattice. Here, we report the emergence of a significant degree of circular polarization of excitons in such a hetero-structure upon non-resonant driving with a linearly polarized laser. The effect is present at zero magnetic field, and sensibly reacts on perpendicularly applied magnetic field. The giant magnitude of polarization, which cannot be explained by conventional birefringence or optical activity of the twisted lattice, suggests a kinematic origin arising from an emergent pyromagnetic symmetry in our structure, which we exploit to gain insight into the microscopic processes of our device.
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Submitted 20 May, 2021;
originally announced May 2021.
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Direct control of high magnetic fields for cold atom experiments based on NV centers
Authors:
Alexander Hesse,
Kerim Köster,
Jakob Steiner,
Julia Michl,
Vadim Vorobyov,
Durga Dasari,
Jörg Wrachtrup,
Fred Jendrzejewski
Abstract:
In cold atomic gases the interactions between the atoms are directly controllable through external magnetic fields. The magnetic field control is typically performed indirectly by stabilizing the current through a pair of Helmholtz coils, which produce this large bias field. Here, we overcome the limitations of such an indirect control through a direct feedback scheme, which is based on nitrogen-v…
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In cold atomic gases the interactions between the atoms are directly controllable through external magnetic fields. The magnetic field control is typically performed indirectly by stabilizing the current through a pair of Helmholtz coils, which produce this large bias field. Here, we overcome the limitations of such an indirect control through a direct feedback scheme, which is based on nitrogen-vacancy centers acting as a magnetic field sensor. This allows us to measure and stabilize fields of 4.66 mT down to 12 nT RMS noise over the course of 24 h, measured on a 1 Hz bandwidth. We achieve a control of better than 1 ppm after 20 minutes of integration time, ensuring high long-term stability for experiments. This approach extends direct magnetic field control to strong magnetic fields, which could enable new precise quantum simulations in this regime.
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Submitted 4 February, 2021; v1 submitted 18 March, 2020;
originally announced March 2020.
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Exciton-polaritons in flatland: Controlling flatband properties in a Lieb lattice
Authors:
Tristan H. Harder,
Oleg A. Egorov,
Johannes Beierlein,
Philipp Gagel,
Johannes Michl,
Monika Emmerling,
Christian Schneider,
Ulf Peschel,
Sven Höfling,
Sebastian Klembt
Abstract:
In recent years, novel two-dimensional materials such as graphene, bismuthene and transition-metal dichalcogenides have attracted considerable interest due to their unique physical properties. A range of physical effects can be transferred to the realms of photonics by creating artificial photonic lattices emulating these two-dimensional materials. Here, exciton-polaritons in semiconductor microca…
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In recent years, novel two-dimensional materials such as graphene, bismuthene and transition-metal dichalcogenides have attracted considerable interest due to their unique physical properties. A range of physical effects can be transferred to the realms of photonics by creating artificial photonic lattices emulating these two-dimensional materials. Here, exciton-polaritons in semiconductor microcavities offer an exciting opportunity to study a part-light, part-matter quantum fluid of light in a complex lattice potential. In this paper, we study exciton-polaritons in a two-dimensional Lieb lattice of buried optical traps. The $S$ and $P_{xy}$ photonic orbitals of such a Lieb lattice give rise to the formation of two flatbands which are of greatest interest for the distortion-free storage of compact localized states. By using a well controlled etch-and-overgrowth technique, we manage to control the trapping as well as the site couplings with great precision. This allows us to spectroscopically monitor the flatness of the flatbands across the full Brillouin zone. Furthermore, we demonstrate experimentally that these flatbands can be directly populated by condensation under non-resonant laser excitation. Finally, using this advanced device approach we demonstrate resonant and deterministic excitation of flatband modes in transmission geometry. Our findings establish the exciton-polariton systems as a highly controllable, optical many-body system to study flatband effects and for distortion-free storage of compact localized states.
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Submitted 13 February, 2020;
originally announced February 2020.
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Robust and accurate electric field sensing with solid state spin ensembles
Authors:
Julia Michl,
Jakob Steiner,
Andrej Denisenko,
Andre Buelau,
Andre Zimmermann,
Kazuo Nakamura,
Hitoshi Sumiya,
Shinobu Onoda,
Philipp Neumann,
Junichi Isoya,
Joerg Wrachtrup
Abstract:
Electron spins in solids constitute remarkable quantum sensors. Individual defect centers in diamond were used to detect individual nuclear spins with nanometer scale resolution, and ensemble magnetometers rival SQUID and vapor cell magnetometers when taking into account room temperature operation and size. NV center spins can also detect electric field vectors, despite their weak coupling to elec…
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Electron spins in solids constitute remarkable quantum sensors. Individual defect centers in diamond were used to detect individual nuclear spins with nanometer scale resolution, and ensemble magnetometers rival SQUID and vapor cell magnetometers when taking into account room temperature operation and size. NV center spins can also detect electric field vectors, despite their weak coupling to electric fields. %even that of an isolated fundamental charge, despite their weak coupling to electric fields. Here, we employ ensembles of NV center spins to measure macroscopic AC electric vector fields with high precision. We utilize low strain, $^{12}$C enriched diamond to achieve maximum sensitivity and tailor the spin Hamiltonian via proper magnetic field adjustment to map out the AC electric field strength and polarization and arrive at refined electric field coupling constants. For high precision measurements we combine classical lock-in detection with aspects from quantum phase estimation for effective suppression of technical noise. Eventually, this enables $t^{-1/2}$ uncertainty scaling of the electric field strength over extended averaging periods, enabling us to reach a sensitivity down to $10^{-7}$ V/$μ$m.
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Submitted 6 January, 2019;
originally announced January 2019.
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Nanoscale spin manipulation with pulsed magnetic gradient fields from a hard disc drive writer
Authors:
Sven Bodenstedt,
Ingmar Jakobi,
Julia Michl,
Ilja Gerhardt,
Philipp Neumann,
Jörg Wrachtrup
Abstract:
The individual and coherent control of solid-state based electron spins is important covering fields from quantum information processing and quantum metrology to material research and medical imaging. Especially for the control of individual spins in nanoscale networks, the generation of strong, fast and localized magnetic fields is crucial. Highly-engineered devices that demonstrate most of the d…
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The individual and coherent control of solid-state based electron spins is important covering fields from quantum information processing and quantum metrology to material research and medical imaging. Especially for the control of individual spins in nanoscale networks, the generation of strong, fast and localized magnetic fields is crucial. Highly-engineered devices that demonstrate most of the desired features are found in nanometer size magnetic writers of hard disk drives (HDD). Currently, however, their nanoscale operation, in particular, comes at the cost of excessive magnetic noise. Here, we present HDD writers as a tool for the efficient manipulation of single as well as multiple spins. We show that their tunable gradients of up to 100 μT/nm can be used to spectrally address individual spins on the nanoscale. Their GHz Bandwidth allows to switch control fields within nanoseconds, faster than characteristic timescales such as Rabi and Larmor periods, spin-spin couplings or optical transitions, thus extending the set of feasible spin manipulations. We used the fields to drive spin transitions through non-adiabatic fast passages or enable the optical readout of spin states in strong misaligned fields. Building on these techniques, we further apply the large magnetic field gradients for microwave selective addressing of single spins and show its use for the nanoscale optical colocalization of two emitters.
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Submitted 15 August, 2018; v1 submitted 9 April, 2018;
originally announced April 2018.
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Efficient creation of dipolar coupled nitrogen-vacancy spin qubits in diamond
Authors:
Ingmar Jakobi,
Seyed Ali Momenzadeh,
Felipe Fávaro de Oliveira,
Julia Michl,
Florestan Ziem,
Matthias Schreck,
Philipp Neumann,
Andrej Denisenko,
Jörg Wrachtrup
Abstract:
Coherently coupled pairs or multimers of nitrogen-vacancy defect electron spins in diamond have many promising applications especially in quantum information processing (QIP) but also in nanoscale sensing applications. Scalable registers of spin qubits are essential to the progress of QIP. Ion implantation is the only known technique able to produce defect pairs close enough to allow spin coupling…
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Coherently coupled pairs or multimers of nitrogen-vacancy defect electron spins in diamond have many promising applications especially in quantum information processing (QIP) but also in nanoscale sensing applications. Scalable registers of spin qubits are essential to the progress of QIP. Ion implantation is the only known technique able to produce defect pairs close enough to allow spin coupling via dipolar interaction. Although several competing methods have been proposed to increase the resulting resolution of ion implantation, the reliable creation of working registers is still to be demonstrated. The current limitation are residual radiation-induced defects, resulting in degraded qubit performance as trade-off for positioning accuracy. Here we present an optimized estimation of nanomask implantation parameters that are most likely to produce interacting qubits under standard conditions. We apply our findings to a well-established technique, namely masks written in electron-beam lithography, to create coupled defect pairs with a reasonable probability. Furthermore, we investigate the scaling behavior and necessary improvements to efficiently engineer interacting spin architectures.
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Submitted 4 October, 2016;
originally announced October 2016.
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Perfect alignment and preferential orientation of nitrogen-vacancy centers during CVD growth of diamond on (111) surfaces
Authors:
Julia Michl,
Tokuyuki Teraji,
Sebastian Zaiser,
Ingmar Jakobi,
Gerald Waldherr,
Florian Dolde,
Philipp Neumann,
Marcus W. Doherty,
Neil B. Manson,
Junichi Isoya,
Jörg Wrachtrup
Abstract:
Synthetic diamond production is key to the development of quantum metrology and quantum information applications of diamond. The major quantum sensor and qubit candidate in diamond is the nitrogen-vacancy (NV) color center. This lattice defect comes in four different crystallographic orientations leading to an intrinsic inhomogeneity among NV centers that is undesirable in some applications. Here,…
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Synthetic diamond production is key to the development of quantum metrology and quantum information applications of diamond. The major quantum sensor and qubit candidate in diamond is the nitrogen-vacancy (NV) color center. This lattice defect comes in four different crystallographic orientations leading to an intrinsic inhomogeneity among NV centers that is undesirable in some applications. Here, we report a microwave plasma-assisted chemical vapor decomposition (MPCVD) diamond growth technique on (111)-oriented substrates that yields perfect alignment ($94\pm2%$) of as-grown NV centers along a single crystallographic direction. In addition, clear evidence is found that the majority ($74\pm4%$) of the aligned NV centers were formed by the nitrogen being first included in the (111) growth surface and then followed by the formation of a neighboring vacancy on top. The achieved homogeneity of the grown NV centers will tremendously benefit quantum information and metrology applications.
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Submitted 11 February, 2014; v1 submitted 16 January, 2014;
originally announced January 2014.
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Detection of a single fundamental charge with nanoscale resolution in ambient conditions using the NV$^-$ center in diamond
Authors:
Florian Dolde,
Marcus W. Doherty,
Julia Michl,
Ingmar Jakobi,
Boris Naydenov,
Sebastien Pezzagna,
Jan Meijer,
Philipp Neumann,
Fedor Jelezko,
Neil B. Manson,
Jörg Wrachtrup
Abstract:
Single charge detection with nanoscale spatial resolution in ambient conditions is a current frontier in metrology that has diverse interdisciplinary applications. Here, such single charge detection is demonstrated using two nitrogen-vacancy (NV) centers in diamond. One NV center is employed as a sensitive electrometer to detect the change in electric field created by the displacement of a single…
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Single charge detection with nanoscale spatial resolution in ambient conditions is a current frontier in metrology that has diverse interdisciplinary applications. Here, such single charge detection is demonstrated using two nitrogen-vacancy (NV) centers in diamond. One NV center is employed as a sensitive electrometer to detect the change in electric field created by the displacement of a single electron resulting from the optical switching of the other NV center between its neutral (NV$^0$) and negative (NV$^-$) charge states. As a consequence, our measurements also provide direct insight into the charge dynamics inside the material.
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Submitted 15 October, 2013;
originally announced October 2013.
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Weak localization with nonlinear bosonic matter waves
Authors:
Timo Hartmann,
Josef Michl,
Cyril Petitjean,
Thomas Wellens,
Juan-Diego Urbina,
Klaus Richter,
Peter Schlagheck
Abstract:
We investigate the coherent propagation of dilute atomic Bose-Einstein condensates through irregularly shaped billiard geometries that are attached to uniform incoming and outgoing waveguides. Using the mean-field description based on the nonlinear Gross-Pitaevskii equation, we develop a diagrammatic theory for the self-consistent stationary scattering state of the interacting condensate, which is…
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We investigate the coherent propagation of dilute atomic Bose-Einstein condensates through irregularly shaped billiard geometries that are attached to uniform incoming and outgoing waveguides. Using the mean-field description based on the nonlinear Gross-Pitaevskii equation, we develop a diagrammatic theory for the self-consistent stationary scattering state of the interacting condensate, which is combined with the semiclassical representation of the single-particle Green function in terms of chaotic classical trajectories within the billiard. This analytical approach predicts a universal dephasing of weak localization in the presence of a small interaction strength between the atoms, which is found to be in good agreement with the numerically computed reflection and transmission probabilities of the propagating condensate. The numerical simulation of this quasi-stationary scattering process indicates that this interaction-induced dephasing mechanism may give rise to a signature of weak antilocalization, which we attribute to the influence of non-universal short-path contributions.
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Submitted 31 August, 2012; v1 submitted 23 December, 2011;
originally announced December 2011.