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Massachusetts Institute of Technology

Seth Lloyd

Vittorio Giovannetti

Lorenzo Maccone

Dirk Robert Englund

William D Oliver

Vwani P Roychowdhury

Jacob C Mower

Danna Rosenberg

Mikkel Heuck

Michael F O'Keeffe

Mollie Schwartz

Gabriel Samach

Iman Marvian Mashhad

Jelena Notaros

Morten Kjaergaard

Cosmo Lupo

Amy Greene

Tal Mor

Jose Manuel Fernandez

Yossi Weinstein

Systems and methods for performing open-loop quantum error mitigation using quantum measurement emulations are provided. The open-loop quantum error mitigation methods do not require the performance of state readouts or state tomography, reducing hardware requirements and increasing overall computation speed. To perform a quantum measurement emulation, an error mitigation apparatus is configured to stochastically apply a quantum gate to a qubit or set of qubits during a quantum computational process. The stochastic application of the quantum gate projects the quantum state of the affected qubits onto an axis, reducing a trace distance between the quantum state and a desired quantum state.

Quantum measurement emulation error mitigation protocol for quantum computing

A large-scale tunable-coupling ring array includes an input waveguide coupled to multiple ring resonators, each of which has a distinct resonant wavelength. The collective effect of these multiple ring resonators is to impart a distinct time delay to a distinct wavelength component (or frequency component) in an input signal, thereby carrying out quantum scrambling of the input signal. The scrambled signal is received by a receiver also using a large-scale tunable-coupling ring array. This receiver-end ring resonator array recovers the input signal by imparting a compensatory time delay to each wavelength component. Each ring resonator can be coupled to the input waveguide via a corresponding Mach Zehnder interferometer (MZI). The MZI includes a phase shifter on at least one of its arms to increase the tunability of the ring array.

Apparatus and methods for locked quantum communication using photonic integrated circuits

In a database query operation, a quantum private query (QPQ) protocol allows a user to determine whether the database provider has been trying to obtain information about their query by performing quantum superpositions of different queries in addition to performing normal queries. This means that, in addition to being able to request the jth or the kth records in the database, the user can also request both records in a quantum superposition. To find out whether the database provider is trying to discover her queries, the user sends proper superpositions of queries and then checks the answer provided by the database to determine whether the superposition has been preserved. If superposition has not been preserved, the user can be confident that the database provider has cheated, and has tried to obtain information on the query.

Method for ensuring privacy while querying a database by using quantum superposition and multiple responses

In an address signal decoder for a RAM memory, address signals are decoded in a 'bucket brigade' address decoding architecture in which the address signals or bits are sequentially sent along the same address decoding path. The inventive architecture comprises a set of node switches linked into a binary tree. The address signals enter at the root node of the binary tree. As each address signal reaches a node switch at the end the path, it sets the path direction for that switch node so that subsequent address signals that follow the path will use that path direction. The decoder can be used with classical or quantum RAM memories.

Bucket brigade address decoding architecture for classical and quantum random access memories

A method for decreasing entropy of a quantum system, for example nuclear spins. The quantum system comprising at least two subsystems, a first subsystem of elements with a first relaxation time (hereinafter&#x2014;computation elements) and a second subsystem of elements with a second relaxation time (hereinafter&#x2014;reset elements), the second relaxation time being shorter than the first relaxation time. The method comprises adiabatically decreasing the entropy of the computation elements in the system (by entropy compression, entropy transfer, or both) and increasing the entropy of at least some reset elements, so that the entropy of the subgroup of reset elements is overall increased; and waiting for the total entropy of the subgroup of reset elements to decrease, wherein the above two steps are carried out at least once.

Algorithmic cooling

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Wellesley, MA, United States of America

Seth Lloyd