Ionq, Inc.

University System of Maryland

Shantanu Debnath

Christopher R Monroe

Norbert M Linke

Jason Madjdi Amini

Neal Pisenti

Vandiver Chaplin

Jwo-Sy Chen

Marko Cetina

Kai Hudek

Kristin Marie Beck

Jaime David Wong-Campos

Caroline Figgatt

Melissa Jameson

Jason Hieu Van Nguyen

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.

Optical control of atomic quantum bits for phase control of operation

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.

Correction of light-shift effects in trapped-ion quantum gates

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.

Removing a translation error between a programmed strength and an applied strength of quantum gates

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.

Fast cooling of ion motion in a long chain using local modes

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.

Multi-qubit control with acousto-optic modulators

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.

Optical alignment using reflective dove prisms

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.

Quantum logic gate design and optimization

A method of performing an entangling operation in a chain of trapped ions includes selecting a gate duration value and a detuning value of a pulse sequence used to perform an entangling gate operation on a first ion and a second ion, measuring frequencies of collective motional modes of the chain, computing a value of an entangling interaction between the first and second ions and values of phase space trajectories of the collective motional modes, based on the selected gate duration value, the selected detuning value, and the measured frequencies of the collective motional modes, determining an intensity of each pulse segment in the pulse sequence based on the computed values, generating the pulse sequence by connecting the pulse segments, each pulse segment having the determined intensity and a pulse shape with ramps formed using a spline, and applying the generated pulse sequence to the first and second ions.

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College Park, MD, United States of America

Shantanu Debnath