Josephson transmission lines (JTLs) for superconducting devices and related methods are provided. In one example, a device comprising a JTL for propagating quantum pulses in a first direction in response to an application of a clock signal having a plurality of phases is provided. The JTL may include a first inductive element coupled between a first terminal and a second terminal, a first Josephson junction (JJ) coupled between the second terminal and a ground terminal, a second inductive element coupled between the second terminal and a third terminal, and a second JJ coupled between the third terminal and the ground terminal. The second inductive element is configured to form an inductive loop, and the inductive loop may be configured to operate in a mode such that a quantum pulse cannot travel in a second direction opposite from the first direction regardless of a phase of the clock signal.

Disclosed herein are superconducting qubit devices with Josephson Junctions utilizing resistive switching materials, i.e., resistive Josephson Junctions (RJJs), as well as related methods and quantum circuit assemblies. In some embodiments, an RJJ may include a bottom electrode, a top electrode, and a resistive switching layer (RSL) disposed between the bottom electrode and the top electrode. Using the RSLs in Josephson Junctions of superconducting qubits may allow fine tuning of junction resistance, which is particularly advantageous for optimizing performance of superconducting qubit devices. In addition, RJJs may be fabricated using methods that could be efficiently used in large-scale manufacturing, providing a substantial improvement with respect to approaches for forming conventional Josephson Junctions, such as e.g. double-angle shadow evaporation approach.

A Josephson memory array and logic circuits use quasi-long-Josephson-junction interconnects to propagate signals at fast speeds and low energy expense, while permitting for memory arrays as dense fabrics of relatively simple unit cell sub-circuits, which include it Josephson junctions, connected together by the interconnects. Each of the unit cell sub-circuits can be configured as a looped or linear arrangement. The unit cell sub-circuits and interconnects provide a fast, dense memory technology for reciprocal quantum logic (RQL), suitable for low-level caches and other memories collocated with an RQL processor.

Techniques regarding a DSFQ logic family are provided. For example, one or more embodiments described herein can comprise a system, which can comprise a dynamic single flux quantum logic circuit that has a self-resetting internal state and can be powered by direct current. Further, the self-resetting internal state can be characterized by two time constants.

A method of operating a quantum information processing apparatus is provided. This apparatus includes a structure of coupled qubits, where N3, wherein the structure further includes coupling elements. The coupling elements couple pairs of N qubits, wherein, at least, a portion of the qubits are connected by a respective one of the coupling elements, whereby the two qubits of each said pair are connected by a respective coupling element. A method comprises identifying a path of M qubits in the structure of coupled qubits, wherein the path extends from a first qubit to a last qubit of the N qubits. The identified path consists of M qubits and M1 coupling elements alternating along said path, where 2<MN. A single-cycle operation is performed, wherein all pairs of two successive qubits in the identified path are concomitantly subjected to exchange-type interactions of distinct strengths.

Systems and methods for determining timing paths and reconciling topology in a superconducting circuit design are provided. The design may include a first timing path having a first set of timing pins associated with a first timing constraint group including a first timing endpoint and a second timing endpoint. An example method includes processing the first timing constraint group to assign a first legal start time to the first timing endpoint and a second legal start time to the second timing endpoint. The method further includes inserting a first shadow element representing a first physically connected component on the timing path, where the first shadow element precedes the first timing endpoint or follows the second timing endpoint. The method further includes addressing any changes to the first legal start time or the second legal start time caused by an insertion of the first shadow element on the timing path.

There is described a microwave device and methods of operating same. The device comprises at least one superconducting qubit coupled to a transmission line defining a first port, and a filter. The filter comprises a first resonant element having a first resonance frequency f.sub.1, positioned along the transmission line between the first port and the qubit, and a second resonant element having a second resonance frequency f.sub.2 different from f.sub.1 and positioned along the transmission line between the first resonant element and the qubit.

Systems and methods are provided for a ZZZ coupler. A first tunable coupler is coupled to the first qubit and tunable via a first control signal. A second tunable coupler is coupled to the first tunable coupler to direct a flux of the first qubit into a tuning loop of the second tunable coupler, such that when a first coupling strength associated with the first tunable coupler is non-zero, a second coupling strength, associated with the second tunable coupler, is a function of a second control signal applied to the second tunable coupler and a state of the first qubit. The second qubit and the third qubit are coupled to one another through the second tunable coupler, such that, when the second coupling strength is non-zero it is energetically favorable for the states of the first and second qubits to assume a specific relationship with respect to the Z-axis.

Techniques relate to operating a quantum processing device is provided. The device includes at least two fixed-frequency quantum circuits coupled to a frequency-tunable coupler. The frequency of the coupler can be modulated so as to drive at least two selectively addressable energy transitions in the quantum processing device. The method includes modulating the frequency of the coupler so as to drive two first-order energy transitions. This is done so as to transfer (at least partly) an excitation of one of the quantum circuits to at least another one of the quantum circuits, via the tunable coupler. Related quantum processing devices are also provided.

A qubit includes a superconducting loop interrupted by a plurality of magnetic flux tunneling elements, such as DC SQUIDs, leaving superconducting islands between the elements. An effective transverse magnetic moment is formed by magnetically tuning each element to yield a large tunneling amplitude. The electrical polarization charge on an island is tuned to produce destructive interference between the tunneling amplitudes using the Aharonov-Casher effect, resulting in an effectively zero transverse field. Biasing the charge away from this tuning allows tunneling to resume with a large amplitude. Interrupting the island with a third tunneling path, such as a Josephson junction, permits independently tuning and biasing the two islands that result, enabling effective control of two independent (X and Y) transverse fields.