Nadezhda Kukharchyk

Coherent properties of single rare-earth spin qubits.

Rare-earth-doped crystals are excellent hardware for quantum storage of photons. Additional functionality of these materials is added by their waveguiding properties allowing for on-chip photonic networks. However, detection and coherent properties of rare-earth single-spin qubits have not been demonstrated so far. Here we present experimental results on high-fidelity optical initialization, efficient coherent manipulation and optical readout of a single-electron spin of Ce(3+) ion in a yttrium aluminium garnet crystal. Under dynamic decoupling, spin coherence lifetime reaches T2 = 2 ms and is almost limited by the measured spin-lattice relaxation time T1 = 4.5 ms. Strong hyperfine coupling to aluminium nuclear spins suggests that cerium electron spins can be exploited as an interface between photons and long-lived nuclear spin memory. Combined with high brightness of Ce(3+) emission and a possibility of creating photonic circuits out of the host material, this makes cerium spins an interesting option for integrated quantum photonics.

All-Optical Preparation of Coherent Dark States of a Single Rare Earth Ion Spin in a Crystal.

All-optical addressing and coherent control of single solid-state based quantum bits is a key tool for fast and precise control of ground-state spin qubits. So far, all-optical addressing of qubits was demonstrated only in a very few systems, such as color centers and quantum dots. Here, we perform high-resolution spectroscopic of native and implanted single rare earth ions in solid, namely, a cerium ion in yttrium aluminum garnet (YAG) crystal. We find narrow and spectrally stable optical transitions between the spin sublevels of the ground and excited optical states. Utilizing these transitions we demonstrate the generation of a coherent dark state in electron spin sublevels of a single Ce^{3+} ion in YAG by coherent population trapping.

Hybrid quantum circuit with implanted erbium ions

We report on hybrid circuit quantum electrodynamics experiments with focused ion beam implanted Er3+ ions in Y2SiO5 coupled to an array of superconducting lumped element microwave resonators. The Y2SiO5 crystal is divided into several areas with distinct erbium doping concentrations, each coupled to a separate resonator. The coupling strength is varied from 5 MHz to 18.7 MHz, while the linewidth ranges between 50 MHz and 130 MHz. We confirm the paramagnetic properties of the implanted spin ensemble by evaluating the temperature dependence of the coupling. The efficiency of the implantation process is analyzed and the results are compared to a bulk doped Er:Y2SiO5 sample. We demonstrate the integration of these engineered erbium spin ensembles with superconducting circuits.

Production yield of rare-earth ions implanted into an optical crystal

Rare-earth ions doped into desired locations of optical crystals might enable a range of novel integrated photonic devices for quantum applications. With this aim, we have investigated the production yield of cerium and praseodymium by means of ion implantation. As a measure, the collected fluorescence intensity from both, implanted samples and single centers was used. With a tailored annealing procedure for cerium, a yield up to 53% was estimated. Praseodymium yield amounts up to 91%.

Photoluminescence of focused ion beam implanted Er

Erbium-doped low symmetry Y2SiO5 crystals attract a lot of attention in perspective of quantum information applications. However, only doping of the samples during growth is available up to now, which yields a quite homogeneous doping density. In the present work, we deposit Er3+-ions by the focused ion beam technique at yttrium sites with several fluences in one sample. With a photoluminescence study of these locally doped Er3+:Y2SiO5 crystals, we are able to evaluate the efficiency of the implantation process and develop it for the highest efficiency possible. We observe the dependence of ion activation after the post-implantation annealing on the fluence value. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

^{3+}

Erbium-doped low symmetry Y2SiO5 crystals attract a lot of attention in perspective of quantum information applications. However, only doping of the samples during growth is available up to now, which yields a quite homogeneous doping density. In the present work, we deposit Er3+-ions by the focused ion beam technique at yttrium sites with several fluences in one sample. With a photoluminescence study of these locally doped Er3+:Y2SiO5 crystals, we are able to evaluate the efficiency of the implantation process and develop it for the highest efficiency possible. We observe the dependence of ion activation after the post-implantation annealing on the fluence value. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

:Y

The interaction between intersubband resonances (ISRs) and metamaterial microcavities constitutes a strongly coupled system where new resonances form that depend on the coupling strength. Here we present experimental evidence of strong coupling between the cavity resonance of a terahertz metamaterial and the ISR in a high electron mobility transistor (HEMT) structure. The device is electrically switched from an uncoupled to a strongly coupled regime by tuning the ISR with epitaxially grown transparent gate. The asymmetric potential in the HEMT structure enables ultrawide electrical tuning of ISR, which is an order of magnitude higher as compared to an equivalent square well. For a single heterojunction with a triangular confinement, we achieve an avoided splitting of 0.52 THz, which is a significant fraction of the bare intersubband resonance at 2 THz.

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We present a study on the intersublevel spacings of electrons and holes in a single layer of InAs self-assembled quantum dots. We use Fourier transform infrared transmission spectroscopy via a density chopping scheme for direct experimental observation of the intersublevel spacings of electrons without any external magnetic field. Epitaxial, complementary-doped and semi-transparent electrostatic gates are grown within the ultra high vacuum conditions of molecular beam epitaxy to voltage-tune the device, while a two dimensional electron gas (2DEG) serves as a back contact. Spacings of the hole sublevels are indirectly calculated from the photoluminescence spectrum by using a simple model given by Warburton et al [1]. Additionally, we observe that the intersubb and resonances of the 2DEG are enhanced due to the quantum dot layer on top of the device.

SiO

We explore spin dynamics of isotopically purified

_{5}

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