Abstract: In a general aspect, calibration is performed in a quantum computing system. In some cases, domains of a quantum computing system are identified, where the domains include respective domain control subsystems and respective subsets of quantum circuit devices in a quantum processor of the quantum computing system. Sets of measurements are obtained from one of the domains and stored in memory. Device characteristics of the quantum circuit devices of the domain are obtained based on the set of measurements, and the device characteristics are stored in a memory of the control system. Quantum logic control parameters for the subset of quantum circuit devices of the domain are obtained based on the set of measurements and stored in memory.

Abstract: A coil apparatus and methods for magnetic resonance imaging involving a wire winding, the wire winding having at least one of: a hollow cross-section wire and a solid cross-section wire, the solid cross-section wire having at least one of: a solid small cross-section wire and a solid large cross-section wire, the solid large cross-section wire having a thickness greater than that of the solid small cross-section wire, and the solid small cross-section wire disposed in one of adjacent and proximate at least one of the hollow cross-section wire and the solid large cross-section wire, whereby at least one of current density, winding density, and heat extraction are increasable.

Abstract: Systems and methods for imaging a subject with a magnetic resonance imaging system using magnetic field gradients generated by one or more gradient coils operating with gradient coil settings, such as gradient amplitudes and gradient slew rates, above a threshold at which peripheral nerve stimulation is likely to be induced in the subject. A dielectric assembly is positioned adjacent a skin surface of the subject such that the dielectric assembly attenuates the local electric fields induced by the magnetic field gradients, which would be likely to induce PNS when the dielectric assembly is not arranged adjacent the skin surface of the subject. As a result of the dielectric assembly placed adjacent the skin surface of the subject, the gradient coil settings can be increased above the threshold without inducing PNS in the subject.

Abstract: A system and method for compensation of radiofrequency (RF) spatial encoding misalignment errors due to gradient non-linearity in magnetic resonance imaging is described. The true magnetic field produced by the gradient coils in space are taken into account in order to encode the appropriate frequency band and offset of the RF pulse corresponding to the desired spatial encoding position and thickness. This method is applicable to any positionally (frequency) encoded radiofrequency (RF) pulses including slice or slab excitation pulses, inversion pulses, spin echo (refocusing) pulses and spatial saturation pulses.

Abstract: In a general aspect, an integrated quantum circuit includes a first substrate and a second substrate. The first substrate includes a first surface and a recess formed in the first substrate along the first surface. The recess has a recess surface and is configured to enclose a quantum circuit element. The first substrate includes a first electrically-conductive layer disposed on the first surface and covering at least a portion of the recess surface. The first electrically-conductive layer includes a first superconducting material. The second substrate includes a second surface and a quantum circuit element. The second substrate includes a second electrically-conductive layer on the second surface that includes a second superconducting material. The first substrate is adjacent the second substrate to enclose the quantum circuit device within the recess. The first electrically-conductive layer of the first substrate is electrically-coupled to the second electrically-coupled layer of the second substrate.

Abstract: A method of imaging an implant device in a computing device is provided. The computing device includes a processor interconnected with a memory and a display. The method includes, at the processor: obtaining a first magnetic resonance (MR) image of a patient tissue, the first MR image containing a first magnetic field strength indicator; responsive to the implant device being inserted in the patient tissue, obtaining a second MR image of the patient tissue, the second MR image containing a second magnetic field strength indicator smaller than the first magnetic field strength indicator; registering the second MR image with the first MR image; generating a composite image from the first MR image and the second MR image; and presenting the composite image on the display.

Abstract: A method of imaging an implant device in a computing device is provided. The computing device includes a processor interconnected with a memory and a display. The method includes, at the processor: obtaining a first magnetic resonance (MR) image of a patient tissue, the first MR image containing a first magnetic field strength indicator; responsive to the implant device being inserted in the patient tissue, obtaining a second MR image of the patient tissue, the second MR image containing a second magnetic field strength indicator smaller than the first magnetic field strength indicator; registering the second MR image with the first MR image; generating a composite image from the first MR image and the second MR image; and presenting the composite image on the display.

Abstract: A fat saturation method for a magnetic resonance imaging system having a main magnet providing a magnetic field B0 The method includes: driving a shim coil assembly with a first set of shimming currents to sufficiently alter a B0 field inhomogeneity of the magnetic field B0 within a region that includes a first imaging volume of interest such that water saturation inside the region is reduced from before the first set of shimming currents are applied; applying a fat saturation pulse to the region; identifying the first imaging volume of interest from the region; driving the shim coil assembly with a second set of shimming currents to alter the B0 field inhomogeneity of the magnetic field B0 within the first imaging volume of interest such that the B0 field inhomogeneity within the first imaging volume of interest is reduced; and obtaining magnetic resonance signals from the first imaging volume of interest.

Abstract: In a general aspect, a quantum logic gate is performed in a quantum computing system. In some cases, a pair of qubits are defined in a quantum processor; the pair of qubits can include a first qubit defined by a first qubit device in the quantum processor and a second qubit defined by a tunable qubit device in the quantum processor. A quantum logic gate can be applied to the pair of qubits by communicating a control signal to a control line coupled to the tunable qubit device. The control signal can be configured to modulate a transition frequency of the tunable qubit device at a modulation frequency, and the modulation frequency can be determined based on a transition frequency of the first qubit device.

Abstract: Systems and methods for magnetic field-dependent relaxometry using magnetic resonance imaging (“MRI”) are provided. Relaxation parameters, including longitudinal relaxation time (“T1”) and transverse relaxation time (“T2”), are estimated from magnetic resonance signal data acquired at multiple different magnetic field strengths using the same MRI system. By measuring these relaxation parameters as a function of magnetic field strength, T1 dispersion data, T2 dispersion data, or both, are generated. Based on this dispersion data, quantitative physiological parameters can be estimated. As one example, iron content can be estimated from T2 dispersion data.

Abstract: A portable magnetic resonance imaging (MRI) system and methods, involving a magnet configured to generate a magnetic field, the magnet being a portable magnet transportable on a cart, and at least one coil assembly disposed in relation to the magnet, the at least one coil assembly having at least one gradient coil.

Abstract: A method of manufacturing an electromagnet coil for use in a magnetic resonance imaging (MRI) system includes: generating a coil surface representation defining a surface to contain the electromagnet coil; defining a set of performance metric functions, the set including a mutual inductance function defining mutual inductance between the electromagnet coil and a second electromagnet coil; defining a performance functional based on the coil surface representation and the set of performance metric functions; optimizing the performance functional; generating a current density pattern over the coil surface representation based on the optimized performance functional; and obtaining coil windings defining the electromagnet coil from the current density pattern.

Abstract: Systems and methods involving: a housing having a bore in which a subject to be imaged is placed; a main magnet configured to generate a volume of magnetic field within the bore, the volume of magnetic field having inhomogeneity below a defined threshold; gradient coils configured to linearly vary the volume of magnetic field as a function of spatial location; pulse-generating coils configured to generate and apply radio frequency (RF) pulses to the volume of magnetic field in sequence to scan the portion of the subject; shim gradient coils configured to perturb a spatial distribution of the linearly varying volume of magnetic field; and a control unit configured to operate the gradient coils, pulse-generating coils, and shim gradient coils such that only the user-defined region within the volume of magnetic field is imaged.

Abstract: In a general aspect, a quantum program is automatically synthesized. In some implementations, artificial intelligence systems are used to generate a quantum program to run on a quantum computer. In some aspects, quantum processor output data are generated by a quantum resource executing an initial version of a quantum program, and quantum state information is computed from the quantum processor output data. Neural network input data, which include the quantum state information and a representation of a problem to be solved by the quantum program, are provided to a neural network. Neural network output data are generated by the neural network processing the neural network input data. A quantum logic gate is selected based on the neural network output data. An updated version of the quantum program that includes the selected quantum logic gate is generated.

Abstract: An automatic protocolling system and methods involving a processor operable by way of a set of executable instructions storable in relation to a nontransient memory device, the set of executable instructions configuring the processor to: receive information relating to an initial protocol comprising an initial ordering of a plurality of sequences, the information comprising data relating to an interaction extent value of at least one of an imaging system and a patient as a function of time corresponding to each sequence in the plurality of sequences, the data relating to a time-integrated effect of each sequence in the plurality of sequences; and dynamically determine an alternative protocol comprising an alternative ordering of the plurality of sequences based on the time-integrated effect, whereby an alternative protocol is provided.

Abstract: In a general aspect, calibration is performed in a quantum computing system. In some cases, domains of a quantum computing system are identified, where the domains include respective domain control subsystems and respective subsets of quantum circuit devices in a quantum processor of the quantum computing system. Sets of measurements are obtained from one of the domains and stored in memory. Device characteristics of the quantum circuit devices of the domain are obtained based on the set of measurements, and the device characteristics are stored in a memory of the control system. Quantum logic control parameters for the subset of quantum circuit devices of the domain are obtained based on the set of measurements and stored in memory.

Abstract: A quantum computing system that includes a quantum circuit device having at least one operating frequency; a first substrate having a first surface on which the quantum circuit device is disposed; a second substrate having a first surface that defines a recess of the second substrate, the first and second substrates being arranged such that the recess of the second substrate forms an enclosure that houses the quantum circuit device; and an electrically conducting layer that covers at least a portion of the recess of the second substrate.

Abstract: In a general aspect, a quantum error-correction technique includes applying a first set of two-qubit gates to qubits in a lattice cell, and applying a second, different set of two-qubit gates to the qubits in the lattice cell. The qubits in the lattice cell include data qubits and ancilla qubits, and the ancilla qubits reside between respective nearest-neighbor pairs of the data qubits. After the first and second sets of two-qubit gates have been applied, measurement outcomes of the ancilla qubits are obtained, and the parity of the measurement outcomes is determined.

Abstract: Described here are systems and methods for mitigating or otherwise removing the effects of short-term magnetic field instabilities caused by oscillations of the cold head in a cryogen-free magnet system used for magnetic resonance systems, such as magnetic resonance imaging (“MRI”) systems, nuclear magnetic resonance (“NMR”) systems, or the like.

Abstract: Systems and methods for imaging a subject with a magnetic resonance imaging system using magnetic field gradients generated by one or more gradient coils operating with gradient coil settings, such as gradient amplitudes and gradient slew rates, above a threshold at which peripheral nerve stimulation is likely to be induced in the subject. A dielectric assembly is positioned adjacent a skin surface of the subject such that the dielectric assembly attenuates the local electric fields induced by the magnetic field gradients, which would be likely to induce PNS when the dielectric assembly is not arranged adjacent the skin surface of the subject. As a result of the dielectric assembly placed adjacent the skin surface of the subject, the gradient coil settings can be increased above the threshold without inducing PNS in the subject.