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.

Abstract: Aspects of the present disclosure describe techniques for optical alignment using a reflective dove prism. For example, a system for optical alignment is described that includes an assembly having a housing with three separate, reflecting structures positioned to produce three reflections of one or more laser beams or one or more images, and a controller configured to control a rotation of the assembly about a pivot point to produce a tilt in orientation of the one or more lasers beams or the one or more images that is twice an angle of rotation of the assembly. Another system and a method for aligning laser beams using a housing with three separate, reflecting structures in a trapped ion quantum information processing (QIP) system are also described.

Abstract: A method of performing a computational process using a quantum computer includes generating a laser pulse sequence comprising a plurality of laser pulse segments used to perform an entangling gate operation on a first trapped ion and a second trapped ion of a plurality of trapped ions that are aligned in a first direction, each of the trapped ions having two frequency-separated states defining a qubit, and applying the generated laser pulse sequence to the first and second trapped ions. Each of the plurality of laser pulse segments has a pulse shape with ramps formed using a spline at a start and an end of each of the plurality of laser pulse segments.

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 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 optical alignment using a reflective dove prism. For example, a system for optical alignment is described that includes an assembly having a housing with three separate, reflecting structures positioned to produce three reflections of one or more laser beams or one or more images, and a controller configured to control a rotation of the assembly about a pivot point to produce a tilt in orientation of the one or more lasers beams or the one or more images that is twice an angle of rotation of the assembly. Another system and a method for aligning laser beams using a housing with three separate, reflecting structures in a trapped ion quantum information processing (QIP) system are also described.

Abstract: A method of performing a computational process using a quantum computer includes generating a laser pulse sequence comprising a plurality of laser pulse segments used to perform an entangling gate operation on a first trapped ion and a second trapped ion of a plurality of trapped ions that are aligned in a first direction, each of the trapped ions having two frequency-separated states defining a qubit, and applying the generated laser pulse sequence to the first and second trapped ions. Each of the plurality of laser pulse segments has a pulse shape with ramps formed using a spline at a start and an end of each of the plurality of laser pulse segments.