Iqm Finland Oy

Johannes Heinsoo

Jani Tuorila

Mikko Möttönen

Caspar Ockeloen-Korppi

Olli Ahonen

Jami Rönkkö

Jaakko Salo

Juha Hassel

Tianyi Li

Kok Wai Chan

Kuan Yen Tan

Pasi Lähteenmäki

Wei Liu

Manjunath Ramachandrappa Venkatesh

Jorge Santos

Vasilii Sevriuk

Jukka Räbinä

The invention is generally related to the field of quantum computing and particularly to a tunable resonator-resonator coupling circuit that provides both direct and indirect couplings between linear or nonlinear resonators. The indirect coupling is provided by using a tunable coupling element that comprises two ungrounded superconducting islands. Since the superconducting islands are ungrounded, it is possible to provide different signs of coupling frequencies for the resonators and the superconducting islands, which in turn allows the interaction between the first and second resonators to be controlled more efficiently. Moreover, the design, calibration, and operation of the circuit with such a tunable coupling element are significantly easier and simpler compared to the existing analogues, while providing the same or even better performance. A quantum computing apparatus using one or more such circuits is also provided.

Tunable resonator-resonator coupling circuit and quantum computing apparatus comprising thereof

A quantum electronics circuit comprises quantum circuit elements, control signal lines, and signal couplings therebetween for coupling at least some control signal lines with at least some quantum circuit elements. There are at least a first subset and a second subset of control signal lines. The signal couplings couple each of at least a subgroup of the quantum circuit elements with a respective control signal line of the first subset and a respective control signal line of the second subset. This enables additively controlling states of individual quantum circuit elements of the subgroup with mutually additive control signals transmitted through the respective control signal lines of the first and second subsets.

Additive control of qubits for enabling time-domain and frequency-domain mutiplexing

A tunable coupler for making a controllable coupling to at least a first qubit is disclosed. The tunable coupler includes a first constant coupling element and a tunable coupling element. The first constant coupling element forms a non-galvanic coupling interface to at least the first qubit at a first extremity that is distant from the tunable coupling element. The tunable coupling element is located adjacent to a non-galvanic coupling interface formed as an interface to a circuit element at a second extremity thereof.

Tunable coupler with coupling extension

A superconducting circuit comprises a first and second magnetic-flux-tunable elements. Each of these has a respective flux-sensitive part. First and second current-driven superconductive on-chip flux bias lines are provided. Each of these passes adjacent to the flux-sensitive part of the respective magnetic-flux-tunable element. A first plurality of superconductive stray current paths exists adjacent to the first magnetic-flux-tunable element. A second plurality of superconductive stray current paths exist adjacent to the second magnetic-flux-tunable element. The superconductive stray current paths distribute stray currents originating from the flux line of the other magnetic-flux-tunable element into a respective plurality of stray currents around the respective magnetic-flux-tunable element. This way the stray currents are kept from changing the electric characteristics of the respective magnetic-flux-tunable element.

Superconducting circuit with magnetic-flux-tunable elements, and methods for minimizing flux crosstalk between magnetic flux-tunable elements in superconducting circuits

An arrangement, an apparatus, a quantum computing system, and a method are disclosed for reducing qubit leakage errors. In an example, an apparatus includes a qubit having a ground state and a plurality of excited states. The plurality of excited states include a lowest excited state. An energy difference between the ground state and the lowest excited state corresponds to a first frequency, and an energy difference between the lowest excited state and another excited state in the plurality of excited states corresponds to a second frequency. The apparatus also includes an energy dissipation structure to dissipate transferred energy, and a filter having a stopband and a passband. The filter is coupled to the qubit and to the energy dissipation structure. The stopband includes the first frequency and the passband includes the second frequency for reducing qubit leakage errors.

Qubit leakage error reductions

It is an objective to provide an arrangement for reducing qubit leakage errors in a quantum computing system. According to an embodiment, an arrangement for reducing qubit leakage errors includes a first qubit and a second qubit selectively couplable to each other. The arrangement also includes an energy dissipation structure that is selectively couplable to the first qubit. The energy dissipation structure is configured to dissipate energy transferred from the first qubit. The arrangement further includes a control unit configured to perform a first quantum operation to transfer a property of a quantum state from the first qubit to the second qubit, couple the first qubit to the energy dissipation structure for a time interval, and perform a second quantum operation to transfer the property of the quantum state from the second qubit to the first qubit after the time interval.

Qubit leakage error reduction

Growing community of inventors

Espoo, Finland

Johannes Heinsoo