Interaction induced non-reciprocal three-level quantum transport

Besides its fundamental importance, non-reciprocity has also found many potential applications in quantum technology. Recently, many quantum systems have been proposed to realize non-reciprocity, but stable non-reciprocal process is still experimentally difficult in general, due to the needed cyclical interactions in artificial systems or operational difficulties in solid state materials. Here, we propose a new kind of interaction induced non-reciprocal operation, based on the conventional stimulated-Raman-adiabatic-passage (STIRAP) setup, which removes the experimental difficulty of requiring cyclical interaction, and thus it is directly implementable in various quantum systems. Furthermore, we also illustrate our proposal on a chain of three coupled superconducting transmons, which can lead to a non-reciprocal circulator with high fidelity without a ring coupling configuration as in the previous schemes or implementations. Therefore, our protocol provides a promising way to explore fundamental non-reciprocal quantum physics as well as realize non-reciprocal quantum device.

Quantum Secure Multiparty Computation with Symmetric Boolean Functions

We propose a class of n-variable Boolean functions which can be used to implement quantum secure multiparty computation.We also give an implementation of a special quantum secure multiparty computation protocol.An advantage of our protocol is that only 1 qubit is needed to compute the n-tuple pairwise AND function,which is more efficient comparing with previous protocols.We demonstrate our protocol on the IBM quantum cloud platform,with a probability of correct output as high as 94.63%.Therefore,our protocol presents a promising generalization in realization of various secure multipartite quantum tasks.

Variational quantum algorithms for scanning the complex spectrum of non-Hermitian systems

Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be complex.Here,we propose a variational quantum algorithm for solving the non-Hermitian Hamiltonian by minimizing a type of energy variance,where zero variance can naturally determine the eigenvalues and the associated left and right eigenstates.Moreover,the energy is set as a parameter in the cost function and can be tuned to scan the whole spectrum efficiently by using a two-step optimization scheme.Through numerical simulations,we demonstrate the algorithm for preparing the left and right eigenstates,verifying the biorthogonal relations,as well as evaluating the observables.We also investigate the impact of quantum noise on our algorithm and show that its performance can be largely improved using error mitigation techniques.Therefore,our work suggests an avenue for solving non-Hermitian quantum many-body systems with variational quantum algorithms on near-term noisy quantum computers.

Dynamical-corrected nonadiabatic geometric quantum computation

Recently,nonadiabatic geometric quantum computation has been received great attentions,due to its fast operation and intrinsic error resilience.However,compared with the corresponding dynamical gates,the robustness of implemented nonadiabatic geometric gates based on the conventional single-loop geometric scheme still has the same order of magnitude due to the requirement of strict multi-segment geometric controls,and the inherent geometric fault-tolerance characteristic is not fully explored.Here,we present an effective geometric scheme combined with a general dynamical-corrected technique,with which the super-robust nonadiabatic geometric quantum gates can be constructed over the conventional single-loop geometric and two-loop composite-pulse geometric strategies,in terms of resisting the systematic error,i.e.,σ_(x)error.In addition,combined with the decoherence-free subspace(DFS)coding,the resulting geometric gates can also effectively suppress theσ_(z)error caused by the collective dephasing.Notably,our protocol is a general one with simple experimental setups,which can be potentially implemented in different quantum systems,such as Rydberg atoms,trapped ions and superconducting qubits.These results indicate that our scheme represents a promising way to explore large-scale fault-tolerant quantum computation.

Nonadiabatic geometric quantum computation with optimal control on superconducting circuits

Quantum gates,which are the essent ial building blocks of quantum computers,are very fragile.Thus,to realize robust quanturm gates with high fidelity is the ultimate goal of quantum manipulation.Here,we propose a nonadiabatic geometric quantum computation scheme on superconducting circuits to engineer arbitrary quantum gates,which share both the robust merit of geometric phases and the capacity to combine with optimal control technique to further enhance the gate robustness.Specif-ically,in our proposal,arbitrary geometric single-qubit gates can be realized on a transmon qubit,by a resonant microwave field driving,with both the amplitude and phase of the driving being time-dependent.Meanwhile,nontrivial two-qubit gometric gates can be implemented by two capacitively coupled transmon qubits,with one of the transmon qubits'frequency being modulated to obtain ef-fective resonant coupling between them.Therefore,our scheme provides a promising step towards fault-tolerant solid-state quantum computation.

Noncyclic nonadiabatic holonomic quantum gates via shortcuts to adiabaticity

High-fidelity quantum gates are essential for large-scale quantum computation.However,any quantum manipulation will inevitably affected by noises,systematic errors and decoherence effects,which lead to infidelity of a target quantum task.Therefore,implementing high-fidelity,robust and fast quantum gates is highly desired.Here,we propose a fast and robust scheme to construct high-fidelity holonomic quantum gates for universal quantum computation based on resonant interaction of three-level quantum systems via shortcuts to adiabaticity.In our proposal,the target Hamiltonian to induce noncyclic non-Abelian geometric phases can be inversely engineered with less evolution time and demanding experimentally,leading to high-fidelity quantum gates in a simple setup.Besides,our scheme is readily realizable in physical system currently pursued for implementation of quantum computation.Therefore,our proposal represents a promising way towards fault-tolerant geometric quantum computation.

Experimental realization of nonadiabatic holonomic single‐qubit quantum gates with two dark paths in a trapped ion

For circuit-based quantum computation,experimental implementation of a universal set of quantum logic gates with high-fidelity and strong robustness is essential and central.Quantum gates induced by geometric phases,which depend only on global properties of the evolution paths,have built-in noise-resilience features.Here,we propose and experimentally demonstrate nonadiabatic holonomic single-qubit quantum gates on two dark paths in a trapped ^(171)γδ^(+)ion based on four-level systems with resonant drives.We confirm the implementation with measured gate fidelity through both quantum process tomography and randomized benchmarking methods.Meanwhile,we find that nontrivial holonomic two-qubit quantum gates can also be realized within current experimental technologies.Compared with previous implementations,our experiments share both the advantages of fast nonadiabatic evolution and robustness against systematic errors.Therefore,our experiments confirm a promising method for fast and robust holonomic quantum computation.

Remote interfacing between superconducting qubits and Rydberg-atom qubits via thermal coupled cavities

We propose a built-in fault-tolerant geometric operation to realize fast remote entanglement between superconducting qubits anchored to a 15 m K plate and Rydberg-atom qubits trapped near a 1 K plate via thermal coupled cavities. We show that this operation is robust against the detrimental effects of the thermal mode states and fluctuations in the control parameters. The operation can generate a high-fidelity entanglement between superconducting and atomic qubits under realistic experimental parameters, comparable to the results of the existing methods using auxiliary cooling systems. The scheme proposed here will promote the development of quantum network and distributed superconducting quantum computation.

Fast quantum state transfer and entanglement for cavity-coupled many qubits via dark pathways

Quantum state transfer(QST)and entangled state generation(ESG)are important building blocks for modern quantum information processing.To achieve these tasks,convention wisdom is to consult the quantum adiabatic evolution,which is time-consuming,and thus is of low fidelity.Here,using the shortcut to adiabaticity technique,we propose a general method to realize high-fidelity fast QST and ESG in a cavity-coupled many qubits system via its dark pathways,which can be further designed for high-fidelity quantum tasks with different optimization purpose.Specifically,with a proper dark pathway,QST and ESG between any two qubits can be achieved without decoupling the others,which simplifies experimental demonstrations.Meanwhile,ESG among all qubits can also be realized in a single step.In addition,our scheme can be implemented in many quantum systems,and we illustrate its implementation on superconducting quantum circuits.Therefore,we propose a powerful strategy for selective quantum manipulation,which is promising in cavity coupled quantum systems and could find many convenient applications in quantum information processing.