Abstract: A method is disclosed, including positioning a lead wire of a gate chip at a distance of less than 10 nm from a semiconductor heterostructure. The heterostructure includes a surface layer and a subsurface layer. The method also includes inducing an electrostatic potential in the subsurface layer by applying a voltage to the lead wire. The method also includes loading a charge carrier into the subsurface layer. The method also includes detecting the charge carrier in the subsurface layer of the semiconductor heterostructure by emitting a radio-frequency pulse using a resonator coupled to the at least one lead wire of the gate chip, detecting a reflected pulse of the emitted radio-frequency pulse, and determining a phase shift of the reflected pulse relative to the emitted radio-frequency pulse. The method also includes characterizing the quantum dot by measuring valley splitting of the quantum dot.

Abstract: A method is disclosed, including positioning a lead wire of a gate chip at a distance of less than 10 nm from a semiconductor heterostructure. The heterostructure includes a surface layer and a subsurface layer. The method also includes inducing an electrostatic potential in the subsurface layer by applying a voltage to the lead wire. The method also includes loading a charge carrier into the subsurface layer. The method also includes detecting the charge carrier in the subsurface layer of the semiconductor heterostructure by emitting a radio-frequency pulse using a resonator coupled to the at least one lead wire of the gate chip, detecting a reflected pulse of the emitted radio-frequency pulse, and determining a phase shift of the reflected pulse relative to the emitted radio-frequency pulse. The method also includes characterizing the quantum dot by measuring valley splitting of the quantum dot.

Abstract: An always-on, exchange-only (AEON) qubit is comprised of three two-level systems (e.g., semiconductor quantum dot or other spin encoded qubit) and can be operated at a “sweet spot” during both single qubit and two-qubit gate operations. The “sweet spot” operation is immune to variations in noise with respect to nontrivial detuning parameters defining the AEON. By operating at the “sweet spot,” both single and two-qubit gate operations can be performed using only exchange pulses (e.g., DC voltage pulses applied to tunneling gates).

Abstract: An always-on, exchange-only (AEON) qubit is comprised of three two-level systems (e.g., semiconductor quantum dot or other spin encoded qubit) and can be operated at a “sweet spot” during both single qubit and two-qubit gate operations. The “sweet spot” operation is immune to variations in noise with respect to nontrivial detuning parameters defining the AEON. By operating at the “sweet spot,” both single and two-qubit gate operations can be performed using only exchange pulses (e.g., DC voltage pulses applied to tunneling gates).

Abstract: Physical superconducting qubits are controlled according to an “encoded” qubit scheme, where a pair of physical superconducting qubits constitute an encoded qubit that can be controlled without the use of a microwave signal. For example, a quantum computing system has at least one encoded qubit and a controller. Each encoded qubit has a pair of physical superconducting qubits capable of being selectively coupled together. Each physical qubit has a respective tunable frequency. The controller controls a state of each of the pair of physical qubits to perform a quantum computation without using microwave control signals. Rather, the controller uses DC-based voltage or flux pulses.

Abstract: Physical superconducting qubits are controlled according to an “encoded” qubit scheme, where a pair of physical superconducting qubits constitute an encoded qubit that can be controlled without the use of a microwave signal. For example, a quantum computing system has at least one encoded qubit and a controller. Each encoded qubit has a pair of physical superconducting qubits capable of being selectively coupled together. Each physical qubit has a respective tunable frequency. The controller controls a state of each of the pair of physical qubits to perform a quantum computation without using microwave control signals. Rather, the controller uses DC-based voltage or flux pulses.