Sub-millisecond Entanglement and iSWAP Gate between Molecular Qubits

Abstract

Quantum computation (QC) and simulation rely on long-lived qubits with controllable interactions. Early work in quantum computing made use of molecules because of their readily available intramolecular nuclear spin coupling and chemical shifts, along with mature nuclear magnetic resonance techniques. Subsequently, the pursuit of many physical platforms has flourished. Trapped polar molecules have been proposed as a promising quantum computing platform, offering scalability and single-particle addressability while still leveraging inherent complexity and strong couplings of molecules. Recent progress in the single quantum state preparation and coherence of the hyperfine-rotational states of individually trapped molecules allows them to serve as promising qubits, with intermolecular dipolar interactions creating entanglement. However, universal two-qubit gates have not been demonstrated with molecules. Here, we harness intrinsic molecular resources to implement a two-qubit iSWAP gate using individually trapped $X^1{\Sigma }^{+}$ NaCs molecules. We characterize the innate dipolar interaction between rotational states and control its strength by tuning the polarization of the traps. By allowing the molecules to interact for 664 $\mu$s at a distance of 1.9 $\mu$m, we create a maximally entangled Bell state with a fidelity of 94(3)\%, following postselection to remove trials with empty traps. Using motion-rotation coupling, we measure residual excitation of the lowest few motional states along the axial trapping direction and find them to be the primary source of decoherence. Finally, we identify two non-interacting hyperfine states within the ground rotational level in which we encode a qubit. The interaction is toggled by transferring between interacting and non-interacting states to realize an iSWAP gate. We verify the gate performance by measuring its logical truth table.

References in corpus (48)

• A High Phase-Space-Density Gas of Polar Molecules
• Experimental realization of Shor's quantum factoring algorithm using nuclear magnetic resonance
• Superconducting Qubits: Current State of Play
• Quantum computation with trapped polar molecules
• Logical quantum processor based on reconfigurable atom arrays
• A toolbox for lattice spin models with polar molecules
• Realizing a lattice spin model with polar molecules
• Dipolar physics: A review of experiments with magnetic quantum gases
• Quantum Gas of Deeply Bound Ground State Molecules
• Ultracold Molecules in the Ro-Vibrational Triplet Ground State
• Calculation of accurate permanent dipole moments of the lowest ${}^{1,3}{\Sigma }^{+}$ states of heteronuclear alkali dimers using extended basis sets
• Tunable Superfluidity and Quantum Magnetism with Ultracold Polar Molecules
• A new bound on the electron's electric dipole moment
• Implementation of a Quantum Algorithm to Solve Deutsch's Problem on a Nuclear Magnetic Resonance Quantum Computer
• Schemes for robust quantum computation with polar molecules
• Robust dynamical decoupling
• High-fidelity gates with mid-circuit erasure conversion in a metastable neutral atom qubit
• QuantumOptics.jl: A Julia framework for simulating open quantum systems
• Quantum-enhanced sensing of displacements and electric fields with large trapped-ion crystals
• Dipolar Exchange Quantum Logic Gate with Polar Molecules
• Ultracold polar molecules as qudits
• Erasure conversion in a high-fidelity Rydberg quantum simulator
• On-Demand Entanglement of Molecules in a Reconfigurable Optical Tweezer Array
• Second-Scale Nuclear Spin Coherence Time of Trapped Ultracold ${}^{23}$Na${}^{40}$K Molecules
• Assembly of a rovibrational ground state molecule in an optical tweezer
• Probing site-resolved correlations in a spin system of ultracold molecules
• Ultrafast energy exchange between two single Rydberg atoms on the nanosecond timescale
• Complementary classical fidelities as an efficient criterion for the evaluation of experimentally realized quantum operations
• Rotational Coherence Times of Polar Molecules in Optical Tweezers
• Synthetic dimensions in ultracold molecules: quantum strings and membranes
• Forming a single molecule by magnetoassociation in an optical tweezer
• Implementation of Quantum Logic Gates Using Polar Molecules in Pendular States
• Dipolar quantum logic for freely-rotating trapped molecular ions
• Formation of ultracold molecules by merging optical tweezers
• Hyperfine structure of alkali-metal diatomic molecules
• Local Realistic Model for the Dynamics of Bulk-Ensemble NMR Information Processing
• Enriching the quantum toolbox of ultracold molecules with Rydberg atoms
• Observation of Rydberg blockade due to the charge-dipole interaction between an atom and a polar molecule
• Erasure-cooling, control, and hyper-entanglement of motion in optical tweezers
• Seconds-scale coherence on nuclear spin transitions of ultracold polar molecules in 3D optical lattices
• Observation of the Hanbury Brown and Twiss Effect with Ultracold Molecules
• Rydberg atom mediated non-destructive readout of collective rotational states in polar molecule arrays
• Antiferromagnetic bosonic $t$-$J$ models and their quantum simulation in tweezer arrays
• Elliptical polarization for molecular Stark shift compensation in deep optical traps
• Quantum magnetism with ultracold molecules
• Demagnetization dynamics of non-interacting trapped fermions
• Dipolar spin-exchange and entanglement between molecules in an optical tweezer array
• Extended rotational coherence of polar molecules in an elliptically polarized trap

Cited by in corpus (18)

• Long-lived entanglement of molecules in magic-wavelength optical tweezers
• Benchmarking direct and indirect dipolar spin-exchange interactions between two Rydberg atoms
• Long-lived multilevel coherences and spin-1 dynamics encoded in the rotational states of ultracold molecules
• The iSWAP gate with polar molecules: Robustness criteria for entangling operations
• Coherence of Symmetry-Protected Rotational Qubits in Cold Polyatomic Molecules
• A Universal Circuit Set Using the $S_3$ Quantum Double
• DiPolMol-Py: A Python package for calculations for ${}^2\Sigma$ ground-state molecules
• Atom-Molecule Superradiance and Entanglement with Cavity-Mediated Three-Body Interactions
• Magneto-Optical Trapping of a Metal Hydride Molecule
• High-fidelity quantum state control of a polar molecular ion in a cryogenic environment
• Formation of ultracold ${}^{39}$K${}^{133}$Cs Feshbach molecules
• Translational dynamics of diatomic molecule in magnetic quadrupole trap
• Scalable platform for qudit-based quantum computing using polar molecules
• Control of Dipolar Dynamics by Geometrical Programming
• High-sensitivity molecular spectroscopy of SrOH using magneto-optical trapping
• Strongly dipolar molecular Bose-Einstein condensates: From few- to many-body physics
• Parity-Doublet Coherence Times in Optically Trapped Polyatomic Molecules
• Photon-mediated entanglement between spin qubits beyond the dispersive regime