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We present experimental and theoretical results on a new regime in quantum dots in which the filling factor 2 singlet state is replaced by new spin polarized phases. We make use of spin blockade spectroscopy to identify the transition to…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 M. Ciorga , A. Wensauer , M. Pioro-Ladriere , M. Korkusinski , Jordan Kyriakidis , A. S. Sachrajda , P. Hawrylak

We implement silicon quantum dot devices with two layers of gate electrodes using a self-alignment technique, which allows for ultra-small gate lengths and intrinsically perfect layer-to-layer alignment. In a double quantum dot system, we…

Single-shot measurement of the charge arrangement and spin state of a double quantum dot are reported, with measurement times down to ~ 100 ns. Sensing uses radio-frequency reflectometry of a proximal quantum dot in the Coulomb blockade…

Mesoscale and Nanoscale Physics · Physics 2010-04-27 C. Barthel , M. Kjaergaard , J. Medford , M. Stopa , C. M. Marcus , M. P. Hanson , A. C. Gossard

We consider a single electron in a 1D quantum dot with a static slanting Zeeman field. By combining the spin and orbital degrees of freedom of the electron, an effective quantum two-level (qubit) system is defined. This pseudo-spin can be…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Yasuhiro Tokura , Wilfred G. van der Wiel , Toshiaki Obata , Seigo Tarucha

We propose a probabilistic quantum cloning scheme using Greenberger-Horne-Zeilinger states, Bell basis measurements, single-qubit unitary operations and generalized measurements, all of which are within the reach of current technology.…

Quantum Physics · Physics 2009-11-06 Chuan-Wei Zhang , Chuan-Feng Li , Zi-Yang Wang , Guang-Can Guo

We investigate spin states of few electrons in a double quantum dot by coupling them weakly to a magnetic field resilient NbTiN microwave resonator. We observe a reduced resonator transmission if resonator photons and spin singlet states…

Mesoscale and Nanoscale Physics · Physics 2019-05-31 A. J. Landig , J. V. Koski , P. Scarlino , C. Reichl , W. Wegscheider , A. Wallraff , K. Ensslin , T. Ihn

We propose an approach to reconstruct two-electron spin qubit states in semiconductor quantum dots by employing tomographic techniques. This procedure exploits the combination of fast gate operations on electron spins trapped in dots and…

Quantum Physics · Physics 2010-11-19 Zhan Su , Tao Tu , Gang Cao , Guang-Can Guo , Guo-Ping Guo

We demonstrate control of the electron number down to the last electron in tunable few-electron quantum dots defined in catalytically grown InAs nanowires. Using low temperature transport spectroscopy in the Coulomb blockade regime we…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 C. Fasth , A. Fuhrer , L. Samuelson , Vitaly N. Golovach , Daniel Loss

We report the realization of an array of four tunnel coupled quantum dots in the single electron regime, which is the first required step toward a scalable solid state spin qubit architecture. We achieve an efficient tunability of the…

Mesoscale and Nanoscale Physics · Physics 2014-05-27 M. R. Delbecq , T. Nakajima , T. Otsuka , S. Amaha , J. D. Watson , M. J. Manfra , S. Tarucha

We introduce a complete Bell measurement on atomic qubits based on two photon interactions with optical cavities and discrimination of coherent states of light. The dynamical system is described by the Dicke model for two three-level atoms…

Quantum Physics · Physics 2019-02-27 Carlos A. González-Gutiérrez , Juan Mauricio Torres

We propose a Bell measurement free scheme to implement a quantum repeater in GaAs/AlGa double qunatum dot systems.we prove the four pairs of double quantum dots compose an entanglement unit, given the the initial state is singlet states.…

Quantum Physics · Physics 2018-01-19 Xiao-Feng Yi , Peng Xu , Qi Yao , Xianfu Quan

Spin qubits based on interacting spins in double quantum dots have been successfully demonstrated. Readout of the qubit state involves a conversion of spin to charge information, universally achieved by taking advantage of a spin blockade…

We report measurements of spin transitions for GaAs quantum dots in the Coulomb blockade regime, and compare ground and excited state transport spectroscopy to direct measurements of the spin polarization of emitted current. Transport…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 R. M. Potok , J. A. Folk , C. M. Marcus , V. Umansky , M. Hanson , A. C. Gossard

As a possible physical realization of a quantum information processor, a system with stacked self-assembled InAs quantum dots buried in GaAs in adjacent to the channel of a spin field-effect transistor has been proposed. In this system,…

Mesoscale and Nanoscale Physics · Physics 2009-03-19 Kazuya Yuasa , Kosuke Okano , Hiromichi Nakazato , Saori Kashiwada , Kanji Yoh

Recent experiments are reviewed that explore the spin states of a ring-shaped many-electron quantum dot. Coulomb-blockade spectroscopy is used to access the spin degree of freedom. The Zeeman effect observed for states with successive…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 T. Ihn , A. Fuhrer , K. Ensslin , M. Bichler , W. Wegscheider

We study a two-electron quantum dot molecule in a magnetic field by the direct diagonalization of the Hamiltonian matrix. The ground states of the molecule with the total spin S=0 and S=1 provide a possible realization for a qubit of a…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 A. Harju , S. Siljamäki , R. M. Nieminen

We analyze experimentally and theoretically the transport spectra of a gated lateral GaAs double quantum dot containing two holes. The strong spin-orbit interaction present in the hole subband lifts the Pauli spin blockade and allows to map…

We study the spin states of a few-electron quantum dot defined in a two-dimensional electron gas, by applying a large in-plane magnetic field. We observe the Zeeman splitting of the two-electron spin triplet states. Also, the one-electron…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 R. Hanson , L. M. K. Vandersypen , L. H. Willems van Beveren , J. M. Elzerman , I. T. Vink , L. P. Kouwenhoven

Exchange-coupled singlet-triplet spin qubits in two gate-defined double quantum dots are considered theoretically. Using charge density operators to describe the double-dot orbital states, we calculate the Coulomb couplings between the…

Mesoscale and Nanoscale Physics · Physics 2015-05-28 Guy Ramon

We demonstrate high speed manipulation of a few-electron double quantum dot. In the one-electron regime, the double dot forms a charge qubit. Microwaves are used drive transitions between the (1,0) and (0,1) charge states of the double dot.…

Mesoscale and Nanoscale Physics · Physics 2010-10-05 J. R. Petta , A. C. Johnson , J. M. Taylor , A. Yacoby , M. D. Lukin , C. M. Marcus , M. P. Hanson , A. C. Gossard