Microsoft Technology Licensing, LLC

Parsa Hassan Bonderson

Chetan Vasudeo Nayak

Michael Hartley Freedman

Roman Mykolayovych Lutchyn

Torsten Karzig

Roman Bela Bauer

David Alexander Aasen

Alan D Tran

Alexei V Bocharov

Christina Paulsen Knapp

Zhenghan Wang

Matthew Benjamin Hastings

Kirill Shtengel

David J Reilly

Sankar Das Sarma

David Clarke

Michael Zaletel

Andrea Franchini Young

Lukasz Fidkowski

Jeongwan Haah

Peter Krogstrup Jeppesen

Dmitry Igorevich Pikulin

Jason Alicea

Kevin Walker

Aspects of the disclosure include removing a faulty qubit in a quantum circuit. The faulty qubit is determined to be in the quantum circuit, the faulty qubit being associated with a plaquette having other qubits, where adjacent plaquettes are neighboring the plaquette. A route is determined to isolate the plaquette from the adjacent plaquettes. Measurements are caused to be performed on the quantum circuit for the route that isolates the plaquette having the faulty qubit and the other qubits.

Fault tolerant Hastings-Haah codes in the presence of dead qubits

A computing system including a processor configured to receive an indication of one or more dead data qubits and one or more dead auxiliary qubits among qubits included in a quantum computing device. The qubits are arranged in a lattice that includes plaquettes. Each of the plaquettes includes data qubits and auxiliary qubits. The processor is further configured to compute a reduced lattice by, for each of the plaquettes that includes at least one dead data qubit, computing a respective first reduced plaquette that omits the dead data qubit. For each of the plaquettes that includes at least one dead auxiliary qubit, the processor is further configured to compute the reduced lattice at least in part by computing a respective second reduced plaquette that omits the dead auxiliary qubit. The processor is further configured to output instructions to implement an error correction code on the reduced lattice.

Reduction of qubit lattice that includes dead data qubits and auxiliary qubits

A computing system including a quantum computing device that includes Majorana islands at which Majorana zero modes (MZMs) are instantiated. The computing system further includes a controller configured to control the quantum computing device to perform a joint parity measurement at two or more MZMs. The controller is further configured to control the quantum computing device to perform quasiparticle poisoning (QPP) detection at the one or more Majorana islands to thereby generate error data. The error data includes one or more QPP indications associated with the one or more Majorana islands. The controller is further configured to receive the error data from the quantum computing device. The controller is further configured to update an accumulated error state of the one or more Majorana islands based at least in part on the error data, and to perform an update operation based at least in part on the accumulated error state.

Tracking and mitigation of quasiparticle poisoning errors in Majorana quantum computing systems

A computing system including a quantum computing device. The quantum computing device includes a Majorana island, a quantum dot (QD), an electrical ground, and a capacitance sensor. The computing system further includes a controller configured to, in each of a plurality of sampling iterations, control the quantum computing device to electrically couple the Majorana island to the electrical ground, disconnect the Majorana island from the electrical ground, electrically couple the Majorana island to the QD, scan over values of a first plunger gate voltage applied to a first plunger gate and a second plunger gate voltage applied to a second plunger gate, and output quantum capacitance measurements. The controller is further configured to receive the quantum capacitance measurements and determine a measured distribution of resonance regions associated with the sampling iterations. The controller is further configured to identify a minimum-energy resonance region and output the minimum-energy resonance region identification.

Identifying minimum-energy resonance region at Majorana island

A computing system is provided, including a processor configured to identify a plurality of measurement sequences that implement a logic gate. Each measurement sequence may include a plurality of measurements of a quantum state of a topological quantum computing device. The processor may be further configured to determine a respective estimated total resource cost of each measurement sequence of the plurality of measurement sequences. The processor may be further configured to determine a first measurement sequence that has a lowest estimated total resource cost of the plurality of measurement sequences. The topological quantum computing device may be configured to implement the logic gate by applying the first measurement sequence to the quantum state.

Measurement sequence determination for quantum computing device

Apparatus, methods, and systems are disclosed for robust scalable topological quantum computing. Quantum dots are fabricated as van der Waals heterostructures, supporting localized topological phases and non-Abelian anyons (quasiparticles). Large bandgaps provide noise immunity. Three-dot structures include an intermediate quantum dot between two computational quantum dots. With the intermediate quantum dot in an OFF state, quasiparticles at the computational quantum dots can be isolated, with long lifetimes. Alternatively, the intermediate quantum dot can be controlled to decrease the quasiparticle tunneling barrier, enabling fast computing operations. A computationally universal suite of operations includes quasiparticle initialization, braiding, fusion, and readout of fused quasiparticle states, with, optionally, transport or tunable interactions&#x2014;all topologically protected. Robust qubits can be operated without error correction. Quasilinear arrays of quantum dots or qubits can be scaled arbitrarily, up to resource limits, and large-scale topological quantum computers can be realized. Extensive two-dimensional arrays can also be used.

Individually tunable quantum dots in all-van der waals heterostructures

Scalable designs for topological quantum computation

A quantum device is fabricated by forming a network of nanowires oriented in a plane of a substrate to produce a Majorana-based topological qubit. The nanowires are formed from combinations of selective-area-grown semiconductor material along with regions of a superconducting material. The selective-area-grown semiconductor material is grown by etching trenches to define the nanowires and depositing the semiconductor material in the trenches. A side gate is formed in an etched trench and situated to control a topological segment of the qubit.

Side-gating in selective-area-grown topological qubits

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 6zero 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,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.

Quantum computing devices with Majorana Hexon qubits

A quantum device includes a syndrome measurement circuit that implements an correction code using a plurality of Majorana qubit islands. The syndrome measurement circuit is adapted to effect a syndrome measurement by performing a sequence of measurement-only operations, where each one of the measurement-only operations involves at most two of the Majorana qubit islands.

Measurement-only majorana-based surface code architecture

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 obit comprisingMajorana 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.

A fusion outcome quasiparticle may be trapped in a potential well of a topological segment. The fusion outcome quasiparticle may be the product of fusion of a first quasiparticle and a second quasiparticle, where the first and the second quasiparticles are localized at ends of a topological segment. The potential well having the fusion outcome quasiparticle trapped therein and a third quasiparticle may be moved relative to each other such that the potential well and the third quasiparticle are brought toward each other. The quasiparticles may be Majorana modes of a nanowire.

Topological qubit fusion

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.

Growing community of inventors

Santa Barbara, CA, United States of America

Parsa Hassan Bonderson