Abstract: Topological superconductor devices with gates formed in two gate layers are described. A topological superconductor device includes a superconducting wire having a first junction near a first end of the superconducting wire and a second junction near a second end, opposite to the first end. The topological superconductor device further includes: (1) a first side-plunger gate and a second-side plunger gate formed in a first gate layer of the topological superconductor device, (2) a middle-plunger gate formed in the first gate layer of the topological superconductor device, (3) a first cutter gate formed in a second layer, different from the first layer, of the topological superconductor device, and (4) a second cutter gate formed in the second layer of the topological superconductor device. The plunger gates are operable to tune respective sections of the superconducting wire and the cutter gates are operable to open and close the respective junctions.

Abstract: Quantum devices formed from a single superconducting wire having a configurable ground connection are described. An example quantum device, configurable to be grounded, comprises a single superconducting wire having at least a first section and a second section, each of which is configurable to be in a topological phase and at least a third section configurable to be in a trivial phase. The quantum device further comprises semiconducting regions formed adjacent to the single superconducting wire, where the single superconducting wire is configurable to store quantum information in at least four Majorana zero modes (MZMs). The semiconducting regions formed adjacent to the single superconducting wire may be used to measure quantum information stored in the at least four MZMs.

Abstract: Quantum devices with two-sided or single-sided dual-purpose Majorana zero mode (MZM) junctions are described. An example quantum device comprises at least one superconducting island configurable to support at least one pair of Majorana zero modes (MZMs). The quantum device further includes a first conductor configurable to be coupled with at least one MZM of the at least one pair of MZMs, where the first conductor is configurable to be in at least one of a grounded state or a Coulomb blockade state. The quantum device further includes a second conductor configurable to be coupled with the at least one MZM of the at least one pair of MZMs, where the second conductor is configurable to be in at least one of a grounded state or a Coulomb blockade state.

Abstract: Quantum devices with chains of quantum dots for controlling tunable couplings between Majorana zero modes (MZMs) are described. Methods for controlling tunable couplings between MZMs using such chains of quantum dots are also described. An example quantum device comprises at least one superconducting island configurable to support at least one pair of Majorana zero modes (MZMs). The quantum device may further include a region adjacent to at least one MZM of the at least one pair of MZMs, where the region is configurable to realize a chain of quantum dots for controlling a tunable coupling between the at least one MZM of the at least one pair of MZMs and another MZM.

Abstract: Provided is a method of determining a gate capacitance of a semiconductor device having a source, a drain, a gate, and a channel, the semiconductor device being arranged in a circuit further comprising an electrical resonator, wherein one of the source, the drain, and the gate is connected to the electrical resonator. The method comprises: measuring a resonance frequency of the circuit; and calculating, based on the resonance frequency, the gate capacitance. Since it is not necessary to pass a current through the semiconductor device, an accurate measurement of gate capacitance may be achieved. Also provided are an apparatus for determining a gate capacitance, a probe for measuring gate capacitance, and a related computer program product.