Research

The development of new technologies at scales approaching the quantum regime is driving new theoretical and experimental research on control in quantum systems. The implementation of quantum control has an enormous impact on a wide range of fields such as chemistry, nuclear magnetic resonance, microelectronics, and precision metrology. Quantum control finds an ideal application in quantum information processing (QIP), which promises to radically improve the acquisition, transmission, and processing of information. To reach this goal it is necessary to improve both the experimental techniques and the coherent control theory of quantum bits (qubits), as well as to gain a deeper knowledge of the mechanisms of decoherence, which must be studied and fought against.
The Quantum Engineering Group focuses on methods to control quantum systems that can deliver QIP devices (not only quantum computers but also simulators, measuring and communication devices), which exceed the capacities of the corresponding classical devices.

Funding

NSF	ARO - MURI QuISM	AFOSR	ONR	NIST	DARPA

The Quantum Engineering Group is part of the Research Lab of Electronics (RLE), the Center for Ultracold Atoms (CUA) and the Interdisciplinary Quantum Information Science and Engineering (iQuISE).

Research Projects

Control of Spin Qubits
	The Nitrogen-Vacancy center has recently emerged as a versatile tool for magnetic resonance,quantum optics, precision measurement and quantum information processing. The system comprising the NV electronic spin and close-by nuclear spins (N and 13C) is an excellent candidate for the implementation of small quantum registers capable of simple quantum algorithms with very high fidelities. These quantum registers can then in turn be connected via photon entanglement or direct dipole-dipole coupling to build a large scale quantum information processor.
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	Quantum control of nuclear spins in diamond Nuclear spins hold promise as a robust quantum memory thanks to their exceptional coherence properties; however, control of nuclear spins is usually slow. We achieve fast control of the nuclear spin with the help of a strongly coupled electronic spin and demonstrate this technique using the nitrogen nuclear spin and electronic spin associated with a nitrogen vacancy center in diamond. We also work on developing and demonstrating simple quantum algorithms in this small quantum register, such as feedback-based protection algorithm using the nuclear spin as an ancilla qubit. Team: Masashi Hirose, Chen Mo
	Turning impurities into quantum resources Electronic spin impurities are the dominant source of noise for quantum systems in the solid-state. We aim to turn these impurities into quantum resources useful for processing quantum information and measuring weak magnetic fields associated with individual atoms. Our system is a single nitrogen-vacancy center in diamond interacting with an ensemble of few electronic spins. To this effort, we develop novel control protocols to probe their dynamics, modulate their evolution, and prepare their states beyond thermal equilibrium. Team: Alexandre Cooper, Calvin Sun, Akira Sone
	Time-optimal control Fast and high fidelity control of quantum systems is a key ingredient for quantum computation and sensing devices. We explore a broad array of strategies to achieve this goal, from coherent feedback control, to indirect control via a quantum actuator to strong driving achieving time-optimal solutions. Our focus is to implement control strategies that implement the desired manipulation, while protecting the quantum system from the deleterious effects of noise and decoherence. Team: Clarice Aiello, Masashi Hirose
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Quantum Sensing & Metrology
	In recent years metrology and quantum information science have emerged as complementary areas of research. We aim at applying the principles of quantum information science to the development of nano-scale magnetic field sensors based on single spin qubits in diamond. We focus on improving the diamond magnetometer readout, enhancing its coherence, improving its spatial resolution and devising strategies to achieve sensitivity beyond the Heisenberg limit. Ideas and techniques from quantum information science are critical in achieving these goals, from quantum non-demolition measurement, to dynamical decoupling and spin squeezing.
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	Stable and sensitive gyroscopes in diamond Gyroscopes find wide applications in everyday life from navigation and inertial sensing to rotation sensors in hand-held devices and automobiles. Current devices, based on either atomic or solid-state systems, impose a choice between long-time stability and high sensitivity in a miniaturized system. We proposed and are currently building a solid-state spin gyroscope associated with the Nitrogen-Vacancy (NV) centers in diamond to overcome these constraints. Team: Ashok Ajoy, Jean-Christophe Jaskula, Kasturi Saha, Joe Smith
	Single molecule MRI via NV centers in diamond We are working on developing techniques for high-resolution structure determination of single molecules at room temperature, employing nano-scale quantum sensors in diamond. Such nano-scale magnetic resonance imaging (MRI) of single molecules would be a significant tool in the understanding of fundamental biological phenomena and for applications such as drug discovery. Team: Ashok Ajoy, Ulf Bissbort, Yixiang Liu, Luca Marseglia, Kasturi Saha
	Quantum System Identification Quantum system identification aims at the precise and efficient characterization of a quantum system’s Hamiltonian. Hamiltonian identification is a prerequisite task for promising technologies based on the laws of quantum mechanics, such as quantum computation, quantum communication and quantum metrology. We are pursuing efficient control protocols and algorithms to extract unknown parameters that characterize the dynamics of complex quantum systems, via measurements of a quantum probe. Team: Akira Sone, Alexandre Cooper-Roy
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Quantum simulation and transport of quantum information
	A system composed of nuclear or electronic spins could play an important role -complementary to cold atoms and molecules- in the simulation of condensed matter systems. For example, well-known NMR pulse sequences can be used to experimentally simulate the transport of quantum information in room temperature linear chains of spins coupled by the dipolar interaction. We use solid-state NMR to study simulations and information transport in large spin systems. In a complementary approach, we develop photonics structure for distributed quantum architectures.
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	Quantum transport in spin networks: wiring up a quantum computer Tomorrows quantum computers will have distributed architectures - with nodes (qubits) linked by quantum wires. We study robust protocols to achieve high-fidelity quantum information transfer using linear spin chains and implement them using solid-state NMR techniques. We are particularly interested in quantum state transport protocols that are the least experimentally demanding to achieve, working e.g. with mixed state spins at room-and using naturally-occurring spin networks that require the least amount of physical engineering. Team: Ashok Ajoy, Ken Xuan Wei
	Nano-structures in diamond for integrated quantum computing A single photon source is an essential component of many quantum technologies, such as quantum communication systems and all-optical quantum computers. Silicon Vacancy centers (SiV) in diamond show remarkable optical properties at room temperature and it has been proved to be a very efficient source of indistinguishable single photons. To achieve these goals, we fabricate nano-structures in diamond coupled to SiV. These structures are meant to increase light collection from the SiV, paving the way for realization of integrated quantum circuits. Team: Luca Marseglia, Kasturi Saha, Ashok Ajoy
	Quantum simulation and new techniques of Hamiltonian engineering Quantum simulation will be an important application for quantum computers over the next decade. At its heart, quantum simulation involves the experimental engineering of natural Hamiltonians to transform them into the interaction to be simulated. We work on developing several experimental Hamiltonian engineering methods in spin architectures with special emphasis on mitigating decoherence and noise in quantum systems. Team: Ashok Ajoy, Ken Xuan Wei
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