Browsing by Author "Maze, Jeronimo R."

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    Collective enhancement in dissipative quantum batteries
    (2022) Carrasco, Javier; Maze, Jeronimo R.; Hermann-Avigliano, Carla; Barra, Felipe
    We study a quantum battery made out of N nonmutually interacting qubits coupled to a dissipative single electromagnetic field mode in a resonator. We quantify the charging energy, ergotropy, transfer rate, and power of the system, showing that collective enhancements are still present despite losses, and can even increase with dissipation. Moreover, we observe that a performance deterioration due to dissipation can be reduced by scaling up the battery size. This is useful for experimental realizations when controlling the quality of the resonator and the number of qubits are limiting factors.
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    First-Principles Identification of Single Photon Emitters Based on Carbon Clusters in Hexagonal Boron Nitride
    (2021) Jara, Cesar; Rauch, Tomas; Botti, Silvana; Marques, Miguel A. L.; Norambuena, Ariel; Coto, Raul; Castellanos-Aguila, J. E.; Maze, Jeronimo R.; Munoz, Francisco
    A recent study associates carbon with single photon emitters (SPEs) in hexagonal boron nitride (h-BN). This observation, together with the high mobility of carbon in h-BN, suggests the existence of SPEs based on carbon clusters. Here, by means of density functional theory calculations, we studied clusters of substitutional carbon atoms up to tetramers in h-BN. Two different conformations of neutral carbon trimers have zero-point line energies and shifts of the phonon sideband compatible with typical photoluminescence spectra. Moreover, some conformations of two small C clusters next to each other result in photoluminescence spectra similar to those found in the experiments. We also showed that vacancies are unable to reproduce the typical features of the phonon sideband observed in most measurements because of the large spectral weight of low-energy breathing modes, ubiquitous in such defects.
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    High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide
    (2019) Nagy, Roland; Niethammer, Matthias; Widmann, Matthias; Chen, Yu-Chen; Udvarhelyi, Peter; Bonato, Cristian; Hassan, Jawad Ui; Karhu, Robin; Ivanov, Ivan G.; Nguyen Tien Son; Maze, Jeronimo R.; Ohshima, Takeshi; Soykal, Oney O.; Gali, Adam; Lee, Sang-Yun; Kaiser, Florian; Wrachtrup, Joerg
    Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin-optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron-phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its (4)A(2) symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with similar to 1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum network applications using semiconductor-based spin-to-photon interfaces and coherently coupled nuclear spins.
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    Low-Temperature Photophysics of Single Nitrogen-Vacancy Centers in Diamond
    (2022) Happacher, Jodok; Broadway, David A.; Bocquel, Juanita; Reiser, Patrick; Jimenez, Alejandro; Tschudin, Marta A.; Thiel, Lucas; Rohner, Dominik; Puigibert, Marcel li Grimau; Shields, Brendan; Maze, Jeronimo R.; Jacques, Vincent; Maletinsky, Patrick
    We investigate the magnetic field dependent photophysics of individual nitrogen-vacancy (NV) color centers in diamond under cryogenic conditions. At distinct magnetic fields, we observe significant reductions in the NV photoluminescence rate, which indicate a marked decrease in the optical readout efficiency of the NV???s ground state spin. We assign these dips to excited state level anticrossings, which occur at magnetic fields that strongly depend on the effective, local strain environment of the NV center. Our results offer new insights into the structure of the NVs??? excited states and a new tool for their effective characterization. Using this tool, we observe strong indications for strain-dependent variations of the NV???s orbital g factor, obtain new insights into NV charge state dynamics, and draw important conclusions regarding the applicability of NV centers for low-temperature quantum sensing.
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    Perfect conductor and mu-metal enhancement of effects in electromagnetic fields over single emitters near topological insulators
    (2024) Dvorquez, Eitan; Pavez, Benjamin; Sun, Qiang; Pinto, Felipe; Greentree, Andrew D.; Gibson, Brant C.; Maze, Jeronimo R.
    We focus on the transmission and reflection coefficients of light in systems involving topological insulators (TIs). Due to the electromagnetic coupling in TIs, new mixing coefficients emerge, leading to new components of the electromagnetic fields of propagating waves. We have discovered a simple heterostructure that provides a 100-fold enhancement of the mixing coefficients for TI materials. Such effect depends on the TI's wave impedance and the selected material for the sublayer. We also predict a transverse deviation of the Poynting vector due to these mixed coefficients contributing to the radiative electromagnetic field of an electric dipole. Given an optimal configuration of the dipole-TI system, this deviation could amount to 0.28% of the Poynting vector due to emission near nontopological materials, making this effect detectable.
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    Photophysics of a single quantum emitter based on vanadium phthalocyanine molecules
    (2024) Escalante, Richard A.; Athpal, Mohan C.; Ruiz-Tagle, Catalina; Lvarado, Vicente H.; Pinto, Felipe; Martinez, Luis J.; Gence, Loik; Garcia, Griselda; Gonzalez, Iyan A.; Maze, Jeronimo R.
    Single quantum emitters play a fundamental role in the development of quantum technologies such as quantum repeaters, and quantum information processing. Isolating individual molecules with stable optical emission is an essential step for these applications, especially for those molecules that present large coherence times at room temperature. Among them, vanadium-oxide phthalocyanine (VOPc) molecules stand out as promising candidates due to the large coherence times of their ground state electronic spin, which are on the order of microseconds when measured in the ensemble. However, the optical properties of such VOPc molecules at the single emitter level have not yet been reported. Here we show that single VOPc molecules with stable optical properties at room temperature can be isolated. We find that the optical response of the molecule under laser illumination of different polarizations agrees well with a system having pyramidal C4vsymmetry. 4 v symmetry. Furthermore, we provide theoretical calculations that support our experimental findings and provide insight into the role of phonons and the internal electronic structure of the molecule. These results demonstrate that this single paramagnetic molecule can function as a single quantum emitter while displaying optical stability under ambient conditions to have their intrinsic properties investigated.
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    Probabilistic magnetometry with a two-spin system in diamond
    (2021) Coto, Raul; Dinani, Hossein T.; Norambuena, Ariel; Chen, Mo; Maze, Jeronimo R.
    Solid-state magnetometers like the nitrogen-vacancy (NV) center in diamond have been of paramount importance for the development of quantum sensing with nanoscale spatial resolution. The underlying protocol is a Ramsey sequence, that imprints an external static magnetic field into the phase of the quantum sensor, which is subsequently read out. In this theoretical work we propose a sensing scheme that harnesses the hyperfine coupling between the NV center and a nearby nuclear spin to set a post-selection protocol. We show that concentrating valuable sensing information into a single successful measurement yields an improvement in sensitivity over Ramsey in the range of short transverse relaxation times. By considering realistic experimental conditions, we found that the detection of weak magnetic fields in the mu T range can be achieved with a sensitivity of few tens of nTHz(-1/2) at cryogenic temperature (4 K), and mu THz(-1/2) at room temperature.
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    Probing Charge Dynamics in Diamond with an Individual Color Center
    (2021) Gardill, Aedan; Kemeny, Ishita; Cambria, Matthew C.; Li, Yanfei; Dinani, Hossein T.; Norambuena, Ariel; Maze, Jeronimo R.; Lordi, Vincenzo; Kolkowitz, Shimon
    Control over the charge states of color centers in solids is necessary to fully utilize them in quantum technologies. However, the microscopic charge dynamics of deep defects in wide-band-gap semiconductors are complex, and much remains unknown. We utilize a single-shot charge-state readout of an individual nitrogen-vacancy (NV) center to probe the charge dynamics of the surrounding defects in diamond. We show that the NV center charge state can be converted through the capture of holes produced by optical illumination of defects many micrometers away. With this method, we study the optical charge conversion of silicon-vacancy (SiV) centers and provide evidence that the dark state of the SiV center under optical illumination is SiV2-. These measurements illustrate that charge carrier generation, transport, and capture are important considerations in the design and implementation of quantum devices with color centers and provide a novel way to probe and control charge dynamics in diamond.
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    Spin-active single photon emitters in hexagonal boron nitride from carbon-based defects
    (2023) Pinilla, Fernanda; Vasquez, Nicolas; Chacon, Ignacio; Maze, Jeronimo R.; Cardenas, Carlos; Munoz, Francisco
    Most single photon emitters in hexagonal boron nitride have been identified as carbon substitutional defects, forming donor-acceptor systems. Unlike the most studied bulk emitters (i.e. color centers in diamond), these defects have no net spin, or have a single unpaired spin. By means of density functional calculations, we show that two non-adjacent carbon substitutional defects of the same type (i.e. C-B-C-B, and C-N-C-N), can have a triplet groundstate. In particular, one of such defects has a zero phonon line energy of 2.5 eV, and its triplet state is nearly 0.5 eV more stable than its singlet. The mechanism behind the destabilization of the singlet state is related to a larger electrostatic repulsion of a symmetric wave function in a charged lattice.
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    Temperature-Dependent Photophysics of Single NV Centers in Diamond
    (2023) Happacher, Jodok; Bocquel, Juanita; Dinani, Hossein T.; Tschudin, Marta A.; Reiser, Patrick; Broadway, David A.; Maze, Jeronimo R.; Maletinsky, Patrick
    We present a comprehensive study of the temperature- and magnetic-field-dependent photolumine-scence (PL) of individual NV centers in diamond, spanning the temperature-range from cryogenic to ambient conditions. We directly observe the emergence of the NV's room-temperature effective excited-state structure and provide a clear explanation for a previously poorly understood broad quenching of NV PL at intermediate temperatures around 50 K, as well as the subsequent revival of NV PL. We develop a model based on two-phonon orbital averaging that quantitatively explains all of our findings, including the strong impact that strain has on the temperature dependence of the NV's PL. These results complete our understanding of orbital averaging in the NV excited state and have significant implications for the fundamental understanding of the NV center and its applications in quantum sensing.