Wisconsin Alumni Research Foundation

Newsouth Innovations Pty Limited

Mark Gregory Friesen

Mark A Eriksson

Susan Nan Coppersmith

Robert J Joynt

Donald E Savage

Daniel Warren Van Der Weide

Max G Lagally

Paul Powell Rugheimer

Daniel R Ward

Charles George Tahan

Merritt Losert

John King Gamble

Paul Rugheimer

Gate-controlled quantum dots based on silicon-germanium (SiGe) alloy heterostructures are provided. Also provided are quantum computing systems incorporating the gate-controlled quantum dots. The quantum dots are formed in a semiconductor heterostructure in which a SiGe alloy quantum well is sandwiched between SiGe alloy barriers or between Ge barriers. The presence of germanium in the quantum dots increases the average valley splitting for quantum dots confined in the SiGe. As a result, the yield of quantum dots having a sufficiently high valley splitting for device applications is increased by the use of a SiGe alloy in the quantum well.

Silicon-germanium alloy-based quantum dots with increased alloy disorder and enhanced valley splitting

Semiconductor heterostructures, methods of making the heterostructures, and quantum dots and quantum computation devices based on the heterostructures are provided. The heterostructures include a quantum well of strained silicon seeded with a relatively low concentration of germanium impurities disposed between two quantum barriers of germanium or a silicon-germanium alloy. The quantum wells are characterized in that the germanium concentration in the wells has an oscillating profile that increases the valley splitting in the conduction band of the silicon quantum well.

Silicon-germanium heterostructures with quantum wells having oscillatory germanium concentration profiles for increased valley splitting

A quantum computing system and method for performing quantum computation is provided. In some aspects, the system includes at least one charge qubit comprising a quantum dot assembly prepared with a symmetric charge distribution, wherein the symmetric charge distribution is configured to reduce a coupling between the charge qubit and a charge noise source. The system also includes a controller for controlling the at least one charge qubit to perform a quantum computation. The system further includes an output for providing a report generated using information obtained from the quantum computation performed.

System and method for quantum computation using symmetrical charge qubits

A quantum semiconductor device is provided. The quantum semiconductor device includes a quantum heterostructure, a dielectric layer, and an electrode. The quantum heterostructure includes a quantum well layer that includes a first 2DEG region, a second 2DEG region, and a third 2DEG region. A first tunnel barrier exists between the first 2DEG region and the second 2DEG region. A second tunnel barrier exists between the second 2DEG region and the third 2DEG region. A third tunnel barrier exists either between the first 2DEG region and the third 2DEG region. The dielectric layer is formed on the quantum heterostructure. The electrode is formed on the dielectric layer directly above the first tunnel barrier.

Direct tunnel barrier control gates in a two-dimensional electronic system

A spin bus quantum computing architecture includes a spin bus formed of multiple strongly coupled and always on qubits that define a string of spin qubits. A plurality of information bearing qubits are disposed adjacent a qubit of the spin bus. Electrodes are formed to the information bearing qubits and the spin bus qubits to allow control of the establishment and breaking of coupling between qubits to allow control of the establishment and breaking of coupling between each information bearing qubit and the spin bus qubit adjacent to it. The spin bus architecture allows rapid and reliable long-range coupling of qubits.

Spin-bus for information transfer in quantum computing

A semiconductor quantum dot device converts spin information to charge information utilizing an elongated quantum dot having an asymmetric confining potential along its length so that charge movement occurs during orbital excitation. A single electron sensitive electrometer is utilized to detect the charge movement. Initialization and readout can be carried out rapidly utilizing RF fields at appropriate frequencies.

Spin readout and initialization in semiconductor quantum dots

Semiconductor dot devices include a multiple layer semiconductor structure having a substrate, a back gate electrode layer, a quantum well layer, a tunnel barrier layer between the quantum well layer and the back gate, and a barrier layer above the quantum well layer. Multiple electrode gates are formed on the multi-layer semiconductor with the gates spaced from each other by a region beneath which quantum dots may be defined. Appropriate voltages applied to the electrodes allow the development and appropriate positioning of the quantum dots, allowing a large number of quantum dots be formed in a series with appropriate coupling between the dots.

Growing community of inventors

Middleton, WI, United States of America

Mark Gregory Friesen