Yangchao Shen

Quantum implementation of the unitary coupled cluster for simulating molecular electronic structure

In classical computational chemistry, the coupled-cluster ansatz is one of the most commonly used

Time reversal and charge conjugation in an embedding quantum simulator

ab~initio

A dynamic photo-thermal model of carbon dioxide laser tissue ablation

methods, which is critically limited by its non-unitary nature. The unitary modification as an ideal solution to the problem is, however, extremely inefficient in classical conventional computation. Here, we provide the first experimental evidence that indeed the unitary version of the coupled cluster ansatz can be reliably performed in physical quantum system, a trapped ion system. We perform a simulation on the electronic structure of a molecular ion (HeH

Revealing nonclassicality beyond Gaussian states via a single marginal distribution

^+

Experimental quantum simulation of fermion-antifermion scattering via boson exchange in a trapped ion

), where the ground-state energy surface curve is probed, energies of excited-states are studied and the bond-dissociation is simulated non-perturbatively. Our simulation takes advantages from quantum computation to overcome the intrinsic limitations in classical computation and our experimental results indicate that the method is promising for preparing molecular ground-states for quantum simulation.

Corrigendum: Experimental Certification of Random Numbers via Quantum Contextuality

A quantum simulator is an important device that may soon outperform current classical computations. A basic arithmetic operation, the complex conjugate, however, is considered to be impossible to be implemented in such a quantum system due to the linear character of quantum mechanics. Here, we present the experimental quantum simulation of such an unphysical operation beyond the regime of unitary and dissipative evolutions through the embedding of a quantum dynamics in the electronic multilevels of a 171Yb+ ion. We perform time reversal and charge conjugation, which are paradigmatic examples of antiunitary symmetry operators, in the evolution of a Majorana equation without the tomographic knowledge of the evolving state. Thus, these operations can be applied regardless of the system size. Our approach offers the possibility to add unphysical operations to the toolbox of quantum simulation, and provides a route to efficiently compute otherwise intractable quantities, such as entanglement monotones.

Quantum simulation of molecular spectroscopy in trapped-ion device

A dynamic photo-thermal model of carbon dioxide (CO2) laser tissue ablation was developed, based on McKenzie’s three-zone model, with the following improvements: (1) the laser-irradiated tissue from the surface to the inside was divided into a carbonized zone, a dried zone, a dehydrating zone, a thermally damaged wet (TDW) zone and an uncoagulated zone; (2) the carbonized and dried tissues were analyzed as porous media, with convection heat transfer between the vapor from the dehydrating tissue and the porous dried/carbonized tissue taken into account; (3) the interactions of temperature distribution, deposited laser energy distribution and dynamic changes in optical and thermal properties as well as blood perfusion rate were included. The finite difference method was used to solve numerically for the temperature and deposited laser energy fields, and the boundary positions of the zones.

Quantum optical emulation of molecular vibronic spectroscopy using a trapped-ion device

Significance Quantum states possess nonclassical properties inaccessible from classical physics, providing a profound basis of quantum physics and a crucial resource for quantum information technology. We propose a general framework to manifest nonclassicality via single marginal distributions, unlike quantum-state tomography using many marginal distributions, applicable to a broad range of quantum systems. Our approach provides a fundamentally unique insight showing how partial information on a quantum state can be sufficient to confirm nonclassicality and a practical efficiency, yielding conclusive evidence of nonclassicality by directly analyzing experimental data without numerical optimization. Remarkably, our method works regardless of measurement axis for all non-Gaussian states of finite dimension. We also experimentally demonstrate our framework, using motional states of a trapped ion. A standard method to obtain information on a quantum state is to measure marginal distributions along many different axes in phase space, which forms a basis of quantum-state tomography. We theoretically propose and experimentally demonstrate a general framework to manifest nonclassicality by observing a single marginal distribution only, which provides a unique insight into nonclassicality and a practical applicability to various quantum systems. Our approach maps the 1D marginal distribution into a factorized 2D distribution by multiplying the measured distribution or the vacuum-state distribution along an orthogonal axis. The resulting fictitious Wigner function becomes unphysical only for a nonclassical state; thus the negativity of the corresponding density operator provides evidence of nonclassicality. Furthermore, the negativity measured this way yields a lower bound for entanglement potential—a measure of entanglement generated using a nonclassical state with a beam-splitter setting that is a prototypical model to produce continuous-variable (CV) entangled states. Our approach detects both Gaussian and non-Gaussian nonclassical states in a reliable and efficient manner. Remarkably, it works regardless of measurement axis for all non-Gaussian states in finite-dimensional Fock space of any size, also extending to infinite-dimensional states of experimental relevance for CV quantum informatics. We experimentally illustrate the power of our criterion for motional states of a trapped ion, confirming their nonclassicality in a measurement-axis–independent manner. We also address an extension of our approach combined with phase-shift operations, which leads to a stronger test of nonclassicality, that is, detection of genuine non-Gaussianity under a CV measurement.

Entangling Ions through Multiple Transverse Modes on an Ion-Chain

Quantum field theories describe a variety of fundamental phenomena in physics. However, their study often involves cumbersome numerical simulations. Quantum simulators, on the other hand, may outperform classical computational capacities due to their potential scalability. Here we report an experimental realization of a quantum simulation of fermion–antifermion scattering mediated by bosonic modes, using a multilevel trapped ion, which is a simplified model of fermion scattering in both perturbative and non-perturbative quantum electrodynamics. The simulated model exhibits prototypical features in quantum field theory including particle pair creation and annihilation, as well as self-energy interactions. These are experimentally observed by manipulating four internal levels of a 171Yb+ trapped ion, where we encode the fermionic modes, and two motional degrees of freedom that simulate the bosonic modes. Our experiment establishes an avenue towards the efficient implementation of field modes, which may prove useful in studies of quantum field theories including non-perturbative regimes.Simulation of quantum field theory using quantum systems would in principle allow avoidance of the exponential overhead required for classical simulations. Here, the authors use a multilevel trapped ion to simulate the processes of self-interaction and particle-antiparticle creation/annihilation.

Experimental measurement of correlation functions in trapped ions

This corrects the article DOI: 10.1038/srep01627.