We consider two new quantum gate mechanisms based on nuclear spins in hyperpolarized solid $^{129}Xe$ and HCl mixtures and inorganic semiconductors. We propose two schemes for implementing a controlled NOT (CNOT) gate based on nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) from hyperpolarized solid $^{129}Xe$ and HCl mixtures and optically pumped NMR in semiconductors. Such gates might be built up with particular spins addressable based on MRI techniques and optical pumping and optical detection techniques. The schemes could be useful for implementing actual quantum computers in terms of a cellular automata architecture.
The electron and nuclear spins of the shallow donor 31P are promising qubit candidates invoked in many proposed Si-based quantum computing schemes. We have recently shown that the near-elimination of inhomogeneous broadening in highly isotopically enriched 28Si enables an optical readout of both the donor electron and nuclear spins by resolving the donor hyperfine splitting in the near-gap donor bound exciton transitions. We have also shown that pumping these same transitions can very quickly produce large electron and nuclear hyperpolarizations at low magnetic fields, where the equilibrium el…
Current experiments in liquid-state nuclear magnetic resonance quantum computing are limited by low initial polarization. To address this problem, we have investigated the use of optical pumping techniques to enhance the polarization of a 2-qubit NMR quantum computer (13C and 1H in 13CHCl3). To efficiently use the increased polarization, we have generalized the procedure for effective pure state preparation. With this new, more flexible scheme, an effective pure state was prepared with polarization-enhancement of a factor of 10 compared to the thermal state. An implementation of Grover's quant…
We use above-bandgap optical excitation, via a 1047 nm laser, to hyperpolarize the $^{31}$P spins in low-doped (N$_D =6\times10^{15}$ cm$^{-3}$) natural abundance silicon at 4.2 K and 6.7 T, and inductively detect the resulting NMR signal. The $30$ kHz spectral linewidth observed is dramatically larger than the 600 Hz linewidth observed from a $^{28}$Si-enriched silicon crystal. We show that the observed broadening is consistent with previous ENDOR results showing discrete isotope mass effect contributions to the donor hyperfine coupling. A secondary source of broadening is likely due to varia…
Quantum sensors have attracted broad interest in the quest towards sub-micronscale NMR spectroscopy. Such sensors predominantly operate at low magnetic fields. Instead, however, for high resolution spectroscopy, the high-field regime is naturally advantageous because it allows high absolute chemical shift discrimination. Here we propose and demonstrate a high-field spin magnetometer constructed from an ensemble of hyperpolarized ${}^{13}C$ nuclear spins in diamond. The ${}^{13}C$ nuclei are initialized via Nitrogen Vacancy (NV) centers and protected along a transverse Bloch sphere axis for min…
Methods that preserve coherence broadly impact all quantum information processing and metrology applications. Dynamical decoupling methods accomplish this by protecting qubits in noisy environments but are typically constrained to the limit where the qubits themselves are non-interacting. Here we consider the alternate regime wherein the inter-qubit couplings are of the same order as dephasing interactions with the environment. We propose and demonstrate a multi-pulse protocol that protects transverse spin states by suitably Hamiltonian engineering the inter-spin coupling while simultaneously …
We report the observation of long-lived Floquet prethermal states in a bulk solid composed of dipolar-coupled $^{13}$C nuclei in diamond at room temperature. For precessing nuclear spins prepared in an initial transverse state, we demonstrate pulsed spin-lock Floquet control that prevents their decay over multiple-minute long periods. We observe Floquet prethermal lifetimes $T_2'\approx$90.9s, extended >60,000-fold over the nuclear free induction decay times. The spins themselves are continuously interrogated for $\sim$10min, corresponding to the application of $\approx$5.8M control pulses. Th…
We construct a local realistic hidden-variable model that describes the states and dynamics of bulk-ensemble NMR information processing up to about 12 nuclear spins. The existence of such a model rules out violation of any Bell inequality, temporal or otherwise, in present high-temperature, liquid-state NMR experiments. The model does not provide an efficient description in that the number of hidden variables grows exponentially with the number of nuclear spins.
We present a classical model for bulk-ensemble NMR quantum computation: the quantum state of the NMR sample is described by a probability distribution over the orientations of classical tops, and quantum gates are described by classical transition probabilities. All NMR quantum computing experiments performed so far with three quantum bits can be accounted for in this classical model. After a few entangling gates, the classical model suffers an exponential decrease of the measured signal, whereas there is no corresponding decrease in the quantum description. We suggest that for small numbers o…
The quantum nature of bulk ensemble NMR quantum computing --the center of recent heated debate, is addressed. Concepts of the mixed state and entanglement are examined, and the data in a 2 qubit liquid NMR quantum computation are analyzed. It is pointed out that the key problem in the current debate is the understanding of entanglement in a mixed state system. The following points are concluded in this Letter: 1)Density matrix describes the "state" of an average particle in an ensemble. It can not describe the state of an individual particle in an ensemble in detail; 2) Entanglement is a prope…
Here we made an analysis of the principles of a semiconductor NMR quantum computer and its developments. The known variant of an individual-access computer (B. Kane) and alternative solid-state bulk-ensemble approach versions allowing to avoid some difficulties in implementing the first variant are considered.
Dynamic Nuclear Polarization (DNP) is a powerful suite of techniques that deliver multifold signal enhancements in NMR and MRI. The generated athermal spin states can also be exploited for quantum sensing and as probes for many-body physics. Typical DNP methods require use of cryogens, large magnetic fields, and high power microwaves, which are expensive and unwieldy. Nanodiamond particles, rich in Nitrogen-Vacancy (NV) centers, have attracted attention as alternative DNP agents because they can potentially be optically hyperpolarized at room temperature. Indeed the realization of a miniature …
A quantum information processing device, based on bulk solid state NMR of the quasi-one dimensional material hydroxyapatite, is proposed following the magnetic resonance force microscopy work of Yamamoto et al (quant-ph/0009122). In a macroscopic sample of hydroxyapatite, our solid state NMR model yields a limit of 10^8 qubits imposed by physics, while development of current technological considerations should allow an upper bound in the range of hundreds to thousands of qubits.
The existence of quantum correlation (as revealed by quantum discord), other than entanglement and its role in quantum-information processing (QIP), is a current subject for discussion. In particular, it has been suggested that this nonclassical correlation may provide computational speedup for some quantum algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been successfully used as a test bench for many QIP implementations, although it has also been continuously criticized for not presenting entanglement in most of the systems used so far. In this paper, we report a theoret…
We have experimentally demonstrated the interferometric complementarity, which relates the distinguishability $D$ quantifying the amount of which-way (WW) information to the fringe visibility $V$ characterizing the wave feature of a quantum entity, in a bulk ensemble by Nuclear Magnetic Resonance (NMR) techniques. We primarily concern on the intermediate cases: partial fringe visibility and incomplete WW information. We propose a quantitative measure of $D$ by an alternative geometric strategy and investigate the relation between $D$ and entanglement. By measuring $D$ and $V$ independently, it…
We report the first use of "logical labeling" to perform a quantum computation with a room-temperature bulk system. This method entails the selection of a subsystem which behaves as if it were at zero temperature - except for a decrease in signal strength - conditioned upon the state of the remaining system. No averaging over differently prepared molecules is required. In order to test this concept, we execute a quantum search algorithm in a subspace of two nuclear spins, labeled by a third spin, using solution nuclear magnetic resonance (NMR), and employing a novel choice of reference frame t…
We report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field nuclear magnetic resonance (NMR). The hyperpolarization is achieved by optical pumping (OP) of nitrogen vacancy defect centers in diamond accompanied by dynamic nuclear polarization (DNP). The technique harnesses the large optically-induced spin polarization of NV- centers at room temperature, which is many orders of magnitude greater than thermal equilibrium polarization and typically achievable only at sub-Kelvin temperatures. Transfer of the spin polarization to the 13C nuclear spins is accomplis…
Conventional nuclear magnetic resonance (NMR) spectroscopy relies on acquiring signal from a macroscopic ensemble of molecules to gain information about molecular structure and dynamics. Transferring this technique to nanoscale sample sizes would enable molecular analysis without the effects of averaging over spatial and temporal inhomogeneities and without the need for macroscopic volumes of analyte, both inherent to large ensemble measurements. Nanoscale NMR based on nitrogen vacancy (NV) centers inside bulk diamond chips achieves single nuclear spin sensitivity and the resolution required t…
Polarizing nuclear spins is of fundamental importance in biology, chemistry and physics. Methods for hyperpolarizing 13C nuclei from free electrons in bulk, usually demand operation at cryogenic temperatures. Room-temperature approaches targeting diamonds with nitrogen-vacancy (NV) centers could alleviate this need, but hitherto proposed strategies lack generality as they demand stringent conditions on the strength and/or alignment of the magnetic field. We report here an approach for achieving efficient electron->13C spin alignment transfers, compatible with a broad range of magnetic field st…
Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) spectroscopy of bulk quantum materials have provided insight into phenomena such as quantum phase criticality, magnetism, and superconductivity. With the emergence of nanoscale 2-D materials with magnetic phenomena, inductively-detected NMR and NQR spectroscopy are not sensitive enough to detect the smaller number of spins in nanomaterials. The nitrogen-vacancy (NV) center in diamond has shown promise in bringing the analytic power of NMR and NQR spectroscopy to the nanoscale. However, due to depth-dependent formation effi…
Quantum computation is a subject of much theoretical promise, but has not been realized in large scale, despite the discovery of fault-tolerant procedures to overcome decoherence. Part of the reason is that the theoretically modest requirements still present daunting experimental challenges. The goal of this Dissertation is to reduce various resources required for robust quantum computation, focusing on quantum error correcting codes and solution NMR quantum computation. A variety of techniques have been developed, including high rate quantum codes for amplitude damping, relaxed criteria for q…
We demonstrate that CPMG and XYXY decoupling sequences with non-ideal $π$ pulses can reduce dipolar interactions between spins of the same species in solids. Our simulations of pulsed electron spin resonance (ESR) experiments show that $π$ rotations with small ($<$~10\%) imperfections refocus instantaneous diffusion. Here, the intractable N-body problem of interacting dipoles is approximated by the average evolution of a single spin in a changing mean field. These calculations agree well with experiments and do not require powerful hardware. Our results add to past attempts to explain similar …
Low thermal polarization of nuclear spins is a primary sensitivity limitation for nuclear magnetic resonance. Here we demonstrate optically pumped (microwave-free) nuclear spin polarization of $^{13}\mathrm{C}$ and $^{15}\mathrm{N}$ in $^{15}\mathrm{N}$-doped diamond. $^{15}\mathrm{N}$ polarization enhancements up to $-2000$ above thermal equilibrium are observed in the paramagnetic system $\mathrm{N_s}^{0}$. Nuclear spin polarization is shown to diffuse to bulk $^{13}\mathrm{C}$ with NMR enhancements of $-200$ at room temperature and $-500$ at $\mathrm{240~K}$, enabling a route to microwave-f…
Bulk 13C polarization can be strongly enhanced in diamond at room-temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating suitably aligned single-crystals at a ~50 mT field promoting anti-crossings between electronic excited-state levels, followed by shuttling of the sample into a custom-built NMR setup and by subsequent 13C detection. A nuclear polarization of ~0.5% - equivalent to the 13C polarization achievable by thermal polarization at room temperature at fields of ~2000 T - was measured, and its bulk nature determined based on …
Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance (NMR) beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond - a paramagnetic point defect whose spin can be optically polarized at room temperature - has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. Here we overcome this hurdle …
