Abstract: Various embodiments of a modular unit for a topologic qubit and of scalable quantum computing architectures using such modular units are disclosed herein. For example, one example embodiment is a modular unit for a topological qubit comprising 6 Majorana zero modes (MZMs) on a mesoscopic superconducting island. These units can provide the computational MZMs with protection from quasiparticle poisoning. Several possible realizations of these modular units are described herein. Also disclosed herein are example designs for scalable quantum computing architectures comprising the modular units together with gates and reference arms (e.g., quantum dots, Majorana wires, etc.) configured to enable joint parity measurements to be performed for various combinations of two or four MZMs associated with one or two modular units, as well as other operations on the states of MZMs.

Abstract: Embodiments of the disclosed technology comprise methods and/or devices for performing measurements and/or manipulations of the collective state of a set of Majorana quasiparticles/Majorana zero modes (MZMs). Example methods/devices utilize the shift of the combined energy levels due to coupling multiple quantum systems (e.g., in a Stark-effect-like fashion). The example methods can be used for performing measurements of the collective topological charge or fermion parity of a group of MZMs (e.g., a pair of MZMs or a group of 4 MZMs). The example devices can be utilized in any system supporting MZMs.

Abstract: Among the embodiments disclosed herein are example methods for generating all Clifford gates for a system of Majorana Tetron qubits (quasiparticle poisoning protected) given the ability to perform certain 4 Majorana zero mode measurements. Also disclosed herein are example designs for scalable quantum computing architectures that enable the methods for generating the Clifford gates, as well as other operations on the states of MZMs. These designs are configured in such a way as to allow the generation of all the Clifford gates with topological protection and non-Clifford gates (e.g. a ?/8-phase gate) without topological protection, thereby producing a computationally universal gate set. Several possible realizations of these architectures are disclosed.

Abstract: Computing bus devices that enable quantum information to be coherently transferred between conventional qubit pairs are disclosed. A concrete realization of such a quantum bus acting between conventional semiconductor double quantum dot qubits is described. The disclosed device measures the joint (fermion) parity of the two qubits by using the Aharonov-Casher effect in conjunction with an ancillary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two cubits, allows for the production of states in which the qubits are maximally entangled, and for teleporting quantum states between the quantum systems.

Abstract: Computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits are disclosed. A concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit is described. The disclosed device measures the joint (fermion) parity of the two different qubits by using the Aharonov-Casher effect in conjunction with an ancillary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows for the production of states in which the topological and conventional qubits are maximally entangled, and for teleporting quantum states between the topological and conventional quantum systems.

Abstract: A twisted track interferometer (TTI) for producing magic states is disclosed. The spin of ½-vortices may be exploited to produce magic states. The disclosed “twisted track interferometer” is a “topological twist” on the conventional Pabre-Pero interferometer adapted to topological superconductors. In the disclosed TTI, the probe particles may be Josephson vortices (JVs). JVs are estimated to be light and will tunnel more easily than Abrikosov vortices. Also, the disclosed TTI does not require multiple tunneling events. Rather, the JVs are propelled down thin insulating tracks within a 2D topological p-wave superconductor by a Magnus force generated by a tunneling supercurrent across the tracks. The JVs encounter tunneling junctions as they pass into the arms of the TTI.

Abstract: A twisted track interferometer (TTI) for producing magic states is disclosed. The spin of ½-vortices may be exploited to produce magic states. The disclosed “twisted track interferometer” is a “topological twist” on the conventional Pabre-Pero interferometer adapted to topological superconductors. In the disclosed TTI, the probe particles may be Josephson vortices (JVs). JVs are estimated to be light and will tunnel more easily than Abrikosov vortices. Also, the disclosed TTI does not require multiple tunneling events. Rather, the JVs are propelled down thin insulating tracks within a 2D topological p-wave superconductor by a Magnus force generated by a tunneling supercurrent across the tracks. The JVs encounter tunneling junctions as they pass into the arms of the TTI.

Abstract: Computing bus devices that enable quantum information to be coherently transferred between conventional qubit pairs are disclosed. A concrete realization of such a quantum bus acting between conventional semiconductor double quantum dot qubits is described. The disclosed device measures the joint (fermion) parity of the two qubits by using the Aharonov-Casher effect in conjunction with an ancillary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two cubits, allows for the production of states in which the qubits are maximally entangled, and for teleporting quantum states between the quantum systems.

Abstract: Computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits are disclosed. A concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit is described, The disclosed device measures the joint (fermion) parity of the two different qubits by using the Aharonov-Casher effect in conjunction. with an ancillary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows for the production of states in which the topological and conventional qubits are maximally entangled, and for teleporting quantum states between the topological and conventional quantum systems.