arXiv subjects

Maili Liu

Publications and source records attributed to Maili Liu.

14 recordsLinked to original sources

arXiv2015

Simultaneous Acquisition of Multi-nuclei Enhanced NMR/MRI by Solution State Dynamic Nuclear Polarization

Dynamic nuclear polarization (DNP) has become a very important hyperpolarization method because it can dramatically increase the sensitivity of nuclear magnetic resonance (NMR) of various molecules. Liquid-state DNP based on Overhauser effect is capable of directly enhancing polarizations of all kinds of nuclei in the system. The combination of simultaneous Overhauser multi-nuclei enhancements with the multi-nuclei parallel acquisitions provides a variety of important applications in both MR spectroscopy (MRS) and image (MRI). Here we present two simple illustrative examples for simultaneously enhanced multi-nuclear spectra and images to demonstrate the principle and superiority. We have observed very large simultaneous DNP enhancements for different nuclei, such as 1H and 23Na, 1H and 31P, 19F and 31P, especially for the first time to report sodium ion enhancement in liquid. We have also obtained the simultaneous imaging of 19H and 31P at low field by solution-state DNP for the first time. This method can obtain considerably complementary structure-determination information of miscellaneous biomolecules from a single measurement. It can also be used in combination with the fast acquisition schemes and quantitative analysis with reduced scan time.

physics.chem-ph↗

arXiv2005

Quantification of complementarity in multi-qubit systems

Complementarity was originally introduced as a qualitative concept for the discussion of properties of quantum mechanical objects that are classically incompatible. More recently, complementarity has become a \emph{quantitative} relation between classically incompatible properties, such as visibility of interference fringes and "which-way" information, but also between purely quantum mechanical properties, such as measures of entanglement. We discuss different complementarity relations for systems of 2-, 3-, or \textit{n} qubits. Using nuclear magnetic resonance techniques, we have experimentally verified some of these complementarity relations in a two-qubit system.

quant-ph↗

arXiv2004

Realization of decoherence-free subspace using Multiple-Quantum coherences

This letter presents a two-dimensional nuclear magnetic resonance(NMR) approach for constructing a two-logical-qubit decoherence-free subspace (DFS) based on the fact that the three protons in a CH3 spin system can not be resolved in one-dimension NMR spectroscopy, but to a certain extent, can be distinguished by two-dimensional multiple-quantum NMR. We used four noisy physical nuclear spins, including three protons and one carbon in the CH3 spin system, to generate two decoherence-free logical quantum bits. It made full use of the unaddressed spins which could not be used in one-dimensional spectrum. Furthermore, we have experimentally demonstrated such an approach. Our experimental results have shown that our DFS can protect against far more types of decoherence than the one composed of four noisy physical qubits all with different chemical shifts. More importantly, this idea may provide new insights into extending qubit systems in the sense that it effectively utilizes the magnetically equivalent nuclei.

quant-ph↗

arXiv2004

"Spectral Implementation" for creating a labeled pseudo-pure state and the Bernstein-Vazirani's algorithm in a four-qubit nuclear magnetic resonance quantum processor

A quantum circuit is introducted to describe the preparation of a labeled pseudo-pure state by mutiplet-component excitation scheme which has been experimentally implemented on a 4-qubit nuclear magnetic resonance quantum processor. Meanwhile, we theoretically analyze and numerically inverstigate the low-power selective single-pulse implementation of a controlled-rotation gate, which manifests its validity in our experiment. Based on the labeled pseudo-pure state prepared, a 3-qubit Bernstein-Vazirani algorithm has been experimentally demonstrated by spectral implementation. The "answers" of the computations are indentified from the split speak positions in the spectra of the observer spin, which are equivalent to projective measurements required by the algorithms.

quant-ph↗

arXiv2003

Experimental demonstration of the interferometric complementarity of one- and two-particle interference in a bulk Nuclear Magnetic Resonance ensemble

We analyze an interferometric complementarity between one- and two-particle interference in the general case: $V_{i}^{2}+V_{12}^{2}\leq 1$ $(i=1$, $2)$, and further examine the relation among one-particle interference visibility $V_{i}$, two-particle interference visibility $V_{12}$ and the predication $P_{i}$ of the path of a single particle. An equality $V_{i}^{2}+V_{12}^{2}+P_{i}^{2}=1$ $(i=1$, $2)$ is achieved for any pure two-particle source, which implies the condition of the complementarity relation to reach the upper bound and its relation to another interferometric complementarity between path information and interference visibility of a single particle. Meanwhile, the relationships of the complementarities and the entanglement $E$ of the composite system are also investigated. Using nuclear magnetic resonance techniques, the two-particle interferometric complementarity was experimentally tested with the ensemble-averaged spin states, including two extreme cases and an intermediate case.

quant-ph↗

arXiv2003

An interferometric complementarity experiment in a bulk Nuclear Magnetic Resonance ensemble

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 turns out that the duality relation $D^{2}+V^{2}=1$ holds for pure quantum states of the markers.

quant-ph↗

arXiv2003

NMR experimental realization of seventh-order coupling transformations and the seven-qubit modified Deutsch-Jozsa algorithm

We propose a scalable method on the basis of nth-order coupling operators to construct f-dependent phase transformations in the n-qubit modified Deutsch-Jozsa (D-J) quantum algorithm. The novel n-qubit entangling transformations are easily implemented via J-couplings between neighboring spins. The seven-qubit modified D-J quantum algorithm and seventh-order coupling transformations are then experimentally demonstrated with liquid state nuclear magnetic resonance (NMR) techniques. The method may offer the possibility of creating generally entangled states of n qubits and simulating n-body interactions on n-qubit NMR quantum computers.

quant-ph↗

arXiv2002

Nuclear Magnetic Resonance Implemenations of Remote State Preparation of Arbitary Longitudinal Qubit and Remote State Measurement of a Qubit

A qubit chosen from equatorial or polar great circles on a Bloch sphere can be remotely prepared with an Einstain-Podolsky-Rosen (EPR) state shared and a cbit communication. We generalize this protocal into an arbitrary longitudinal qubit on the Bloch sphere in which the azimuthal angle phi can be an arbitrary value instead of only being zero. The generalized scheme was experimentally realized using liquid-state nuclear magnetic resonance (NMR) techniques. Also, we have experimentally demonstrated remote state measurement (RSM) on an arbitary qubit proposed by Pati.

quant-ph↗

arXiv2002

Exhibition of the periodicity of Quantum Fourier Transformation in Nuclear Magnetic Resonance

The remarkable capability of quantum Fourier transformation (QFT) to extract the periodicity of a given periodic function has been exhibited by using nuclear magnetic resonance (NMR) techniques. Two separate sets of experiments were performed. In a full QFT, the periodicity were validated with state tomography and fidelity measurements. For a simplified QFT, the three-qubit pseudo-pure state was created by introducting an additional observer spin, and the spectra recorded on the observer spin showed intuitively the power of QFT\ to find the periodicity. Experimentally realizing the QFT provides a critical step to implement the renowned Shor's quantum factoring algorithm and many other algorithms. Moveover, it can be applied to the study of quantum chaos and other quantum information processing.

quant-ph↗

arXiv2002

Experimental Implementation of Remote State Preparation by Nuclear Magnetic Resonance

We have experimentally implemented remote state preparation (RSP) of a qubit from a hydrogen to a carbon nucleus in molecules of carbon-13 labeled chloroform $^{13}$CHCl$_{3}$ over interatomic distances using liquid-state nuclear magnetic resonance (NMR) technique. Full RSP of a special ensemble of qubits, i.e., a qubit chosen from equatorial and polar great circles on a Bloch sphere with Pati's scheme, was achieved with one cbit communication. Such a RSP scheme can be generalized to prepare a large number of qubit states and may be used in other quantum information processing and quantum computing.

quant-ph↗

arXiv2001

Quantum Computation Based on Magic-Angle-Spinning Solid State Nuclear Magnetic Resonance Spectroscopy

Magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy is shown to be a promising technique for implementing quantum computing. The theory underlying the principles of quantum computing with nuclear spin systems undergoing MAS is formulated in the framework of formalized quantum Floquet theory. The procedures for realizing state labeling, state transformation and coherence selection in Floquet space are given. It suggests that by this method, the largest number of qubits can easily surpass that achievable with other techniques. Unlike other modalities proposed for quantum computing, this method enables one to adjust the dimension of the working state space, meaning the number of qubits can be readily varied. The universality of quantum computing in Floquet space with solid state NMR is discussed and a demonstrative experimental implementation of Grover's search is given.

quant-ph↗

arXiv2001

Experimental realization of 7-qubit universal perfect controlled-NOT and controlled square-root NOT gates

The controlled-NOT gate and controlled square-root NOT gate play an important role in quantum algorithm. This article reports the experimental results of these two universal quantum logic gates (controlled square-root NOT gate and controlled-NOT gate) on a 7-qubit NMR quantum computer. Further, we propose a simple experimental method to measure and correct the error in the controlled phase-shift gate, which is helpful to construct a more perfect phase-shift gate experimentally and can also be used in more qubits discrete Fourier transformation.

quant-ph↗

arXiv2001

Experimental Implementation of Hogg's Algorithm on a Three-Quantum-bit NMR Quantum Computer

Using nuclear magnetic resonance (NMR) techniques with three-qubit sample, we have experimentally implemented the highly structured algorithm for the 1-SAT problem proposed by Hogg. A simplified temporal averaging procedure was employed to the three-qubit spin pseudo-pure state. The algorithm was completed with only a single evaluation of structure of the problem and the solutions were found with probability 100%, which outperform both unstructured quantum and the best classical search algorithm.

quant-ph↗

arXiv2000

Preparation of pseudo-pure states by line-selective pulses in Nuclear Magnetic Resonance

A new method of preparing the pseudo-pure state of a spin system for quantum computation in liquid nuclear magnetic resonance (NMR) was put forward and demonstrated experimentally. Applying appropriately connected line-selective pulses simultaneously and a field gradient pulse techniques we acquired straightforwardly all pseudo-pure states for two qubits in a single experiment much efficiently. The signal intensity with the pseudo-pure state prepared in this way is the same as that of temporal averaging. Our method is suitable for the system with arbitrary numbers of qubits. As an example of application, a highly structured search algorithm----Hogg's algorithm was also performed on the pseudo-pure state $\mid 00>$ prepared by our method.

quant-ph↗