Abstract: A system is provided for imaging trapped ions in a quantum computer. The system includes an ion trap that traps qubit ions and includes electrodes that shuttle individual qubit ions between a first position and a second position spatially different from the first position. The system includes a first imaging lens that collects fluorescence from a qubit ion that is trapped over a surface of the ion trap; a first sensor in a first optical path output from the first imaging lens; a first pick-off mirror in a second optical path output from the first imaging lens that is different than the first optical path; a second imaging lens that collects fluorescence that is reflected from the first pick-off mirror; and a second sensor in a third optical path. Moreover, a controller controls the electrodes to shuttle the qubit ion from the first position to the second position.

Abstract: The disclosure describes various aspects of optical control of atomic quantum bits (qubits) for phase control operations. More specifically, the disclosure describes methods for coherently controlling quantum phases on atomic qubits mediated by optical control fields, applying to quantum logic gates, and generalized interactions between qubits. Various attributes and settings of optical/qubit interactions (e.g., atomic energy structure, laser beam geometry, polarization, spectrum, phase, background magnetic field) are identified for imprinting and storing phase in qubits. The disclosure further describes how these control attributes are best matched in order to control and stabilize qubit interactions and allow extended phase-stable quantum gate sequences.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems. To optimize the performance of QIP systems or quantum computers in terms of both fidelity and algorithm uptime or throughput, described are techniques to stabilize continuous and discrete errors from drifting and/or noisy secondary observables to achieve long term stable operation.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to the correction of light-shift effects in trapped-ion quantum gates. Techniques are described for light-shift correction of single qubit gates when the gates are implemented using counter-propagating Raman laser beams and when the gates are implemented using co-propagating Raman laser beams. Moreover, techniques are also described for light-shift correction of two-qubit gates.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to calibrate compact optical imaging systems that use single atom imaging. A QIP system includes an optical system including an optical relay that receives a beam of light, a housing, and at least one aperture plate. The optical relay includes at least one lens, at least one mirror to fold the beam of light, and a camera sensor to capture at least one image of the beam of light. The housing accommodates the optical relay and includes a slot mechanically referenced to at least one of the lens(es) and the mirror(s). The aperture plate is receivable in the slot. The aperture plate includes an aperture alignable with an optical axis of the optical relay when the aperture plate is received in the slot.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to techniques for removing or correcting for translation errors between a programmed strength and an applied strength of quantum gates. A method is described that includes determining, for each quantum gate in a quantum operation, a non-linearity between an applied strength of a laser beam used for the respective quantum gate and a programmed strength intended to be applied by the laser beam for the respective quantum gate. The method further includes linearizing the non-linearity for each quantum gate and storing linearization information in memory. Moreover, the method includes applying the linearization information to correct for the non-linearity when implementing each quantum gate as part of the quantum operation. A system is also described that is configured to implement the method described above.

Abstract: Aspects of the present disclosure describe techniques for fast cooling of ion motion in a long chain using local motional modes. For example, a method is described for cooling down ions in a chain of ions that includes performing a cooling down sequence in which phonons are removed from the ions in the chain of ions by exciting and de-exciting local motional modes associated with individual ions, wherein sideband transitions that are part of the cooling down sequence are driven faster for the local motional modes than for collective motional modes for the same chain of ions; and completing the cooling down sequence when the local motional modes reach a ground state. A corresponding system and computer-readable storage medium for fast cooling of ion motion in a long chain using local motional modes are also described.

Abstract: Aspects of the present disclosure describe techniques for fast cooling of ion motion in a long chain using local motional modes. For example, a method is described for cooling down ions in a chain of ions that includes performing a cooling down sequence in which phonons are removed from the ions in the chain of ions by exciting and de-exciting local motional modes associated with individual ions, wherein sideband transitions that are part of the cooling down sequence are driven faster for the local motional modes than for collective motional modes for the same chain of ions; and completing the cooling down sequence when the local motional modes reach a ground state. A corresponding system and computer-readable storage medium for fast cooling of ion motion in a long chain using local motional modes are also described.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to the correction of light-shift effects in trapped-ion quantum gates. Techniques are described for light-shift correction of single qubit gates when the gates are implemented using counter-propagating Raman laser beams and when the gates are implemented using co-propagating Raman laser beams. Moreover, techniques are also described for light-shift correction of two-qubit gates.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to the correction of light-shift effects in trapped-ion quantum gates. Techniques are described for light-shift correction of single qubit gates when the gates are implemented using counter-propagating Raman laser beams and when the gates are implemented using co-propagating Raman laser beams. Moreover, techniques are also described for light-shift correction of two-qubit gates.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to a fast single-mode spectroscopy technique that may be used in trapped-ion QIP systems. A method is described that includes performing a first measurement scan (full scan) across all motional modes of an ion chain in a trap followed by a second measurement scan on a single motional mode of the motional modes (single-mode scan). The second measurement scan determines a frequency shift associated with the single motional mode, which is applied to adjust the frequencies of all the motional modes. An implementation of two-qubit gates for quantum computations is based on the adjusted frequencies. A quantum computer or QIP system is also described that is configured to implement and perform the method described above.

Abstract: The disclosure describes various aspects of optical control of atomic quantum bits (qubits) for phase control operations. More specifically, the disclosure describes methods for coherently controlling quantum phases on atomic qubits mediated by optical control fields, applying to quantum logic gates, and generalized interactions between qubits. Various attributes and settings of optical/qubit interactions (e.g., atomic energy structure, laser beam geometry, polarization, spectrum, phase, background magnetic field) are identified for imprinting and storing phase in qubits. The disclosure further describes how these control attributes are best matched in order to control and stabilize qubit interactions and allow extended phase-stable quantum gate sequences.

Abstract: The disclosure describes various aspects of optical control of atomic quantum bits (qubits) for phase control operations. More specifically, the disclosure describes methods for coherently controlling quantum phases on atomic qubits mediated by optical control fields, applying to quantum logic gates, and generalized interactions between qubits. Various attributes and settings of optical/qubit interactions (e.g., atomic energy structure, laser beam geometry, polarization, spectrum, phase, background magnetic field) are identified for imprinting and storing phase in qubits. The disclosure further describes how these control attributes are best matched in order to control and stabilize qubit interactions and allow extended phase-stable quantum gate sequences.

Abstract: A system and method is provided for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to design or configure an optimal side-band cooling operation for trapped ions. A method is described that involves applying a first cooling operation on the trapped ion chain and subsequently applying a second cooling operation on the trapped ion chain that includes applying to each cooling ion in the trapped ion chain, as part of a side-band cooling pulse sequence, at least one analysis pulse followed by a corresponding batch with one or more side-band cooling pulses, wherein each analysis pulse is configured to determine a detuning and pulse duration of the one or more side-band cooling pulses of the corresponding batch. A quantum computer or QIP system is also described that enables the operation of the method described above.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to techniques for removing or correcting for translation errors between a programmed strength and an applied strength of quantum gates. A method is described that includes determining, for each quantum gate in a quantum operation, a non-linearity between an applied strength of a laser beam used for the respective quantum gate and a programmed strength intended to be applied by the laser beam for the respective quantum gate. The method further includes linearizing the non-linearity for each quantum gate and storing linearization information in memory. Moreover, the method includes applying the linearization information to correct for the non-linearity when implementing each quantum gate as part of the quantum operation. A system is also described that is configured to implement the method described above.

Abstract: Aspects of the present disclosure relate generally to systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems, and more particularly, to the correction of light-shift effects in trapped-ion quantum gates. Techniques are described for light-shift correction of single qubit gates when the gates are implemented using counter-propagating Raman laser beams and when the gates are implemented using co-propagating Raman laser beams. Moreover, techniques are also described for light-shift correction of two-qubit gates.

Abstract: Systems and methods for use in the implementation and/or operation of quantum information processing (QIP) systems or quantum computers, and more particularly, to benchmark-driven automation for tuning quantum computers are described. A method includes identifying a set of quantum gates and a number of experimental shots to perform a benchmark algorithm for active stabilization of one or more observables of the set of quantum gates and executing the benchmarking algorithm based on the set of quantum gates and the number of experimental shots. Moreover, in response to the benchmarking algorithm being successful, executing an algorithm on the quantum computer, and in response to the benchmarking algorithm being unsuccessful, iterating the benchmarking algorithm by adjusting the set of quantum gates until the benchmarking algorithm is successful or a preset number of iterations is reached.

Abstract: The disclosure describes various aspects of optical control of atomic quantum bits (qubits) for phase control operations. More specifically, the disclosure describes methods for coherently controlling quantum phases on atomic qubits mediated by optical control fields, applying to quantum logic gates, and generalized interactions between qubits. Various attributes and settings of optical/qubit interactions (e.g., atomic energy structure, laser beam geometry, polarization, spectrum, phase, background magnetic field) are identified for imprinting and storing phase in qubits. The disclosure further describes how these control attributes are best matched in order to control and stabilize qubit interactions and allow extended phase-stable quantum gate sequences.

Abstract: Techniques to address the problem of having micromotion and stray fields affect trapped ions and the operation of QIP systems based on trapped ions are described. For example, one technique or approach may involve collecting scattered photons off the ions using a resonant or near-resonant oscillating electric field (e.g., a laser beam or a microwave source) with some projection in the axis or direction of micromotion that one wishes to reduce. Another technique or approach may include raising and lowering the trapping potentials to see how the ion position changes. The information collected from these techniques may be used to provide appropriate adjustments. Accordingly, the present disclosure describes methods, scripts, or techniques that minimize the effects of micromotion.

Abstract: Aspects of the present disclosure describe techniques for controlling quantum states of ions in an ion chain for a quantum operation. For example, a method is described that includes providing, from a first direction, a global optical beam to the ions in the ion chain, and providing, from a second direction different from the first direction, to each ion in a subset of the ions in the ion chain, a respective addressing optical beam. The method further includes dynamically controlling each of the addressing optical beams being provided by using a respective channel in a multi-channel acousto-optic modulator (AOM) to implement, with the ion chain, one or more quantum gates in a sequence of quantum gates of the quantum operation. Aspects of a quantum information processing (QIP) system that includes the multi-channel AOM for performing the method are also described.