Theory of valley-orbit coupling in a Si/SiGe quantum dot (2009)
Friesen, Mark, Coppersmith, S. N.
Electron states are studied for quantum dots in a strained Si quantum well, taking into account both valley and orbital physics. Realistic geometries are considered, including circular and elliptical...
Valley splitting in a Si/SiGe quantum point contact (2008)
McGuire, L. M., Friesen, Mark, Slinker, K. A., Coppersmith, S. N., Eriksson, M. A.
We present the theory and measurement of valley splitting in a quantum point contact (QPC) in a modulation doped Si/SiGe heterostructure. Our measurements are performed on a submicron Schottky-gated...
Multiscale theory of valley splitting (2008)
Chutia, Sucismita, Coppersmith, S. N., Friesen, Mark
The coupling between $z$ valleys in the conduction band of a Si quantum well arises from phenomena occurring within several atoms from the interface, thus ruling out a theoretical description based...
Dynamic scaling of I}< data for the neutral 2D Coulomb gas Abstract (2007)
Stephen W. Pierson, Mark Friesen
The value of the dynamic critical exponent z has been studied for experimental two-dimensional superconducting and Josephson junction array systems in zero magnetic "eld via the...
Efficient multiqubit entanglement via a spin-bus (2007)
Friesen, Mark, Biswas, Asoka, Hu, Xuedong, Lidar, Daniel
We propose an experimentally feasible architecture with controllable long-range couplings built up from local exchange interactions. The scheme consists of a spin-bus, with strong, always-on...
Controllable valley splitting in silicon quantum devices (2006)
Goswami, Srijit, Slinker, K. A., Friesen, Mark, McGuire, L. M., Truitt, J. L., Tahan, Charles, ...
Silicon has many attractive properties for quantum computing, and the quantum dot architecture is appealing because of its controllability and scalability. However, the multiple valleys in the...
Valley Splitting Theory of SiGe/Si/SiGe Quantum Wells (2006)
Friesen, Mark, Chutia, Sucismita, Tahan, Charles, Coppersmith, S. N.
We present an effective mass theory for SiGe/Si/SiGe quantum wells, with an emphasis on calculating the valley splitting. The theory introduces a valley coupling parameter, $v_v$, which encapsulates...
Elastically Relaxed Free-standing Strained-Si Nanomembranes (2006)
Roberts, Michelle M., Klein, Levente J., Savage, Don E., Slinker, Keith A., Friesen, Mark, Celler, George, ...
Strain plays a critical role in the properties of materials. In silicon and silicon-germanium, strain provides a mechanism for control of both carrier mobility and band offsets. In materials...
Klimeck, Gerhard, Oyafuso, Fabiano, Von Allmen, Paul, Lee, Seungwon, Boykin, Tim, Friesen, Mark, ...
NASA/JPL
Quantum dot quantum computing in Si : lifting degeneracies with strain and confinement (2006)
Boykin, Timothy B., Klimeck, Gerhard, Oyafuso, Fabiano, Von Allmen, Paul, Friesen, Mark, Coppersmith, Susan
NASA/JPL
Conduction band valley splitting in silicon nano-structures (2006)
Klimeck, Gerhard, Boykin, Timothy B., Eriksson, Mark, Friesen, Mark, Coppersmith, Susan N., Von Allmen, Paul, ...
NASA/JPL
Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells (2006)
Friesen, Mark, Eriksson, M. A., Coppersmith, S. N.
The authors investigate the magnetic field dependence of the energy splitting between low-lying valley states for electrons in a Si/SiGe quantum well tilted with respect to the crystallographic axis....
Chutia, Sucismita, Friesen, Mark, Joynt, Robert
Spins in quantum dots can act as the qubit for quantum computation. In this context we point out that spins on neighboring dots will experience an anisotropic form of the exchange coupling, called...
Quantum dots in Si/SiGe 2DEGs with Schottky top-gated leads (2005)
Slinker, K A, Lewis, K L M, Haselby, C C, Goswami, S, Klein, L J, Chu, J O, ...
We report on the fabrication and characterization of quantum dot devices in a Schottky-gated silicon/silicon-germanium two-dimensional electron gas (2DEG). The dots are confined laterally inside an...
Quantum Dots and Etch-Induced Depletion of a Silicon 2DEG (2005)
Klein, L. J., Lewis, K. L. M., Slinker, K. A., Goswami, Srijit, Van Der Weide, D. W., Blick, R. H., ...
The controlled depletion of electrons in semiconductors is the basis for numerous devices. Reactive-ion etching provides an effective technique for fabricating both classical and quantum devices....
Theory of the Stark Effect for P donors in Si (2005)
We develop a multi-valley effective mass theory for substitutional donors in silicon in an inhomogeneous environment. Valley-orbit coupling is treated perturbatively. We apply the theory to the Stark...
Boykin, Timothy B, Klimeck, Gerhard, Friesen, Mark, Coopersmith, S N, Von Allmen, Paul, Oyafuso, Fabiano, ...
A detailed study of reduced-basis tight-binding models of electrons in semiconducting quantum wells is presented. The focus is on systems with degenerate valleys, such as silicon in silicon germanium...
Boykin, Timothy B, Klimeck, Gerhard, Friesen, Mark, Coppersmith, S. N., Von Allmen, Paul, Oyafuso, Fabiano, ...
A detailed study of reduced-basis tight-binding models of electrons in semiconducting quantum wells is presented. The focus is on systems with degenerate valleys, such as silicon in silicon germanium...
Spectroscopy of Valley Splitting in a Silicon/Silicon-Germanium Two-Dimensional Electron Gas (2004)
Goswami, Srijit, Friesen, Mark, Truitt, J. L., Tahan, Charles, Klein, L. J., Chu, J. O., ...
The lifting of the two-fold degeneracy of the conduction valleys in a strained silicon quantum well is critical for spin quantum computing. Here, we obtain an accurate measurement of the splitting of...
Coulomb Blockade in a Silicon/Silicon-Germanium Two-Dimensional Electron Gas Quantum Dot (2004)
Klein, L. J., Slinker, K. A., Truitt, J. L., Goswami, S., Lewis, K. L. M., Coppersmith, S. N., ...
We report the fabrication and electrical characterization of a single electron transistor in a modulation doped silicon/silicon-germanium heterostructure. The quantum dot is fabricated by electron...
Coulomb blockade in a silicon/silicon-germanium two-dimensional electron gas quantum dot (2004)
Klein, L.J., Slinker, K.A., Truitt, J.L., Goswami, S., Lewis, K.L.M., Coppersmith, S.N., ...
This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying...
One-spin quantum logic gates from exchange interactions and a global magnetic field (2003)
Wu, Lian-Ao, Lidar, Daniel A., Friesen, Mark
It has been widely assumed that one-qubit gates in spin-based quantum computers suffer from severe technical difficulties. We show that one-qubit gates can in fact be generated using only modest and...
Valley splitting in strained silicon quantum wells (2003)
Boykin, Timothy B., Klimeck, Gerhard, Eriksson, M. A., Friesen, Mark, Coppersmith, S. N., Von Allmen, Paul, ...
A theory based on localized-orbital approaches is developed to describe the valley splitting observed in silicon quantum wells. The theory is appropriate in the limit of low electron density and...
Spin Readout and Initialization in a Semiconductor Quantum Dot (2003)
Friesen, Mark, Tahan, Charles, Joynt, Robert, Eriksson, M. A.
Electron spin qubits in semiconductors are attractive from the viewpoint of long coherence times. However, single spin measurement is challenging. Several promising schemes incorporate ancillary...
Pseudo-Digital Qubits: A General Approach (2002)
Friesen, Mark, Joynt, Robert, Eriksson, M. A.
Pseudo-digital coupling has recently been proposed as a simple but robust technique for reducing gating errors in quantum dot quantum computers. Here, we discuss the technique in the context of...
Experimental observation of high field diamagnetic fluctuations in Niobium (2002)
Salem-Sugui, S., Friesen, Mark, Alvarenga, A. D., Gandra, F. G., Doria, M. M., ...
We have performed a magnetic study of a bulk metallic sample of Nb with critical temperature $T_{c}=8.5$ K. Magnetization versus temperature (M {\it vs} T) data obtained for fixed magnetic fields...
Pseudo-digital quantum bits (2002)
Friesen, Mark, Joynt, Robert, Eriksson, M. A.
Quantum computers are analog devices; thus they are highly susceptible to accumulative errors arising from classical control electronics. Fast operation--as necessitated by decoherence--makes gating...
Practical design and simulation of silicon-based quantum dot qubits (2002)
Friesen, Mark, Rugheimer, Paul, Savage, Donald E., Lagally, Max G., Van Der Weide, Daniel W., Joynt, Robert, ...
Spins based in silicon provide one of the most promising architectures for quantum computing. A scalable design for silicon-germanium quantum dot qubits is presented. The design incorporates vertical...
Design and proof of concept for silicon-based quantum dot quantum bits (2002)
Friesen, Mark, Rugheimer, Paul, Savage, Donald E., Lagally, Max G., Van Der Weide, Daniel W., Joynt, Robert, ...
Spins based in silicon provide one of the most promising architectures for quantum computing. Quantum dots are an inherently scalable technology. Here, we combine these two concepts into a workable...
Decoherence of electron spin qubits in Si-based quantum computers (2002)
Tahan, Charles, Friesen, Mark, Joynt, Robert
Direct phonon spin-lattice relaxation of an electron qubit bound by a donor impurity or quantum dot in SiGe heterostructures is investigated. The aim is to evaluate the importance of decoherence from...
Comparison of magnetic- and chemical-boundary roughness in magnetic films and multilayers (2002)
Barnes, B.M., Flack, F., Lagally, D.P., Savage, D.E., Friesen, Mark, ...
This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying...
Colonna-Romano, Louis, Pierson, Stephen W., Friesen, Mark
A numerical study of the neutral two-dimensional (2D) lattice Coulomb gas is performed to examine dynamic scaling, finite size effects, and the dynamic critical exponent $z$ of the...
Dynamic scaling of I-V data for the neutral 2D Coulomb gas (1999)
Pierson, Stephen W., Friesen, Mark
The value of the dynamic critical exponent z has been studied for experimental two-dimensional superconducting and Josephson Junction array systems in zero magnetic field via the Fisher-Fisher-Huse...
Two-Phase Region of the Vortex-Solid Melting Transition: 3D XY Theory (1997)
In clean enough samples of the high-$T_c$ oxide materials, the phase transition into the superconducting state occurs along a first order line in the $H$-$T$ plane. This means that a two-phase region...
Universality of glass scaling in a YBa$_2$Cu$_3$O$_{7-\delta}$ thin film (1997)
Moloni, Katerina, Friesen, Mark, Li, Shi, Souw, Victor, Metcalf, P., McElfresh, M.
The universal behavior of the continuous superconducting (glass) phase transition is studied in a YBa$_2$Cu$_3$O$_{7-\delta}$ thin film. A new analysis technique for extracting critical exponents is...
Dynamic Scaling at the Zero-field 2D Superconducting Transition (1997)
Ammirata, S. M., Friesen, Mark, Pierson, Stephen W., Gorham, LeRoy A., Hunnicutt, Jeffrey C., Trawick, M. L., ...
Zero-field current-voltage (I-V) characteristics of a thin ("two-dimensional") $Bi_2Sr_2CaCu_2O_{8+\delta}$ crystal are reported and analyzed in two ways. The "conventional" approach yields ambiguous...
Recent theoretical work has derived the correct form of the Ginzburg-Landau differential equations, for the superconducting order parameter and vector potential, in the presence of a small defect....
3D XY scaling theory of the superconducting phase transition (1997)
The intermediate 3D XY scaling theory of superconductivity at zero and nonzero magnetic fields is developed, based only upon the dimensional hypothesis $B\sim (Length)^{-2}$. Universal as well as...