According to some aspects, a method is provided of operating a circuit quantum electrodynamics system that includes a physical qubit dispersively coupled to a quantum mechanical oscillator, the method comprising applying a first electromagnetic pulse to the physical qubit based on a number state of the quantum mechanical oscillator, wherein the first electromagnetic pulse causes a change in state of the quantum mechanical oscillator, and applying, subsequent to application of the first electromagnetic pulse, a second electromagnetic pulse to the quantum mechanical oscillator that coherently adds or removes energy from the quantum mechanical oscillator.

According to some aspects, a method is provided of operating a circuit quantum electrodynamics system that includes a physical qubit dispersively coupled to a quantum mechanical oscillator, the method comprising applying a first electromagnetic pulse to the physical qubit based on a number state of the quantum mechanical oscillator, wherein the first electromagnetic pulse causes a change in state of the quantum mechanical oscillator, and applying, subsequent to application of the first electromagnetic pulse, a second electromagnetic pulse to the quantum mechanical oscillator that coherently adds or removes energy from the quantum mechanical oscillator.

A resonant circuit to be connected to a negative resistance unit is disclosed. The resonant circuit includes a pair of resonant transmission lines electrically coupled to each other and a coupling transmission line connecting the resonant transmission lines. The resonant transmission lines and the coupling transmission line are formed on a semiconductor substrate. The resonant transmission lines have a length corresponding to a quarter wavelength (/4) of twice of the resonant frequency attributed to the resonant circuit.

An oscillator includes a first package, an oscillation element housed in the first package, a first temperature controller housed in the first package, a second package adapted to house the first package, and a second temperature controller disposed outside the first package, and housed in the second package.

A microwave generator includes a power supply, an output circuit, a feedback oscillator, a pulse controller, a signal combination circuit and a semiconductor amplifier. The power supply converts input voltage and input current into output voltage and output current. The output circuit generates a microwave signal to an output terminal of the microwave generator and a feedback signal according to the microwave signal. The feedback oscillator generates an oscillation signal according to the feedback signal. According to a reference signal, the pulse controller generates a pulse signal. According to the oscillation signal and pulse signal, the signal combination circuit generates a control signal. The semiconductor amplifier generates and adjusts an amplified signal according to the control signal. The output circuit generates the microwave signal according to the amplified signal. The output current is adjusted according to the amplified signal. Consequently, the input current and the input voltage are in phase.

An LC tank circuit, such as an LC tank circuit of a step-tuned voltage controlled oscillator, includes a plurality of switched capacitor banks and one or more inductors. A first switched capacitor bank switch in response to a range of control signals used to control the VCO output across a range of frequencies. A second switched capacitor bank can switch in response to a subset of the range of control signals used to control the VCO output across a subset of the range of frequencies. The control scheme for the first and second switched capacitor banks can improves the linearity of changes in the frequency of the output signal of the VCO.

A differential constructive wave oscillator device including a single, continuous differential transmission line that is arranged into first and second parallel traces in the form of a Mobius loop. The continuous transmission line includes first and second crossover points, each of which provides for a point of inflection between the first and second traces. In each stage of the device, both the first and second traces of the transmission line carry the forward traveling wave signal from a differential input port to a differential output port. Each phase includes a differential delay section that provides for a phase shift between a signal on the first trace and a signal on the second trace. Each phase additionally includes a differential feedback amplifier that amplifies the forward traveling wave signal at the differential output port, generates a differential feedback signal, and routes the differential feedback signal to the differential input port.

An LC tank circuit, such as an LC tank circuit of a step-tuned voltage controlled oscillator, includes a plurality of switched capacitor banks and one or more inductors. A first switched capacitor bank switch in response to a range of control signals used to control the VCO output across a range of frequencies. A second switched capacitor bank can switch in response to a subset of the range of control signals used to control the VCO output across a subset of the range of frequencies. The control scheme for the first and second switched capacitor banks can improves the linearity of changes in the frequency of the output signal of the VCO.

In accordance with an embodiment, a voltage controlled oscillator (VCO) includes a VCO core having a plurality of transistors and a varactor circuit that has a first end coupled to emitter terminals of the VCO core and a second end coupled to a tuning terminal. The varactor circuit includes a capacitance that increases with increasing voltage applied to the tuning terminal with respect to the emitter terminals of the VCO core.

According to some aspects, a method is provided of operating a system that includes a multi-level quantum system dispersively coupled to a first quantum mechanical oscillator and dispersively coupled to a second quantum mechanical oscillator, the method comprising applying a first drive waveform to the multi-level quantum system, applying one or more second drive waveforms to the first quantum mechanical oscillator, and applying one or more third drive waveforms to the second quantum mechanical oscillator.