Robust storage qubits in ultracold polar molecules

Abstract

Quantum states with long-lived coherence are essential for quantum computation, simulation and metrology. The nuclear spin states of ultracold molecules prepared in the singlet rovibrational ground state are an excellent candidate for encoding and storing quantum information. However, it is important to understand all sources of decoherence for these qubits, and then eliminate them, in order to reach the longest possible coherence times. Here, we fully characterise the dominant mechanisms for decoherence of a storage qubit in an optically trapped ultracold gas of RbCs molecules using high-resolution Ramsey spectroscopy. Guided by a detailed understanding of the hyperfine structure of the molecule, we tune the magnetic field to where a pair of hyperfine states have the same magnetic moment. These states form a qubit, which is insensitive to variations in magnetic field. Our experiments reveal an unexpected differential tensor light shift between the states, caused by weak mixing of rotational states. We demonstrate how this light shift can be eliminated by setting the angle between the linearly polarised trap light and the applied magnetic field to a magic angle of $\arccos (1/\sqrt{3})\approx 55^{\circ }$. This leads to a coherence time exceeding 6.9 s (90% confidence level). Our results unlock the potential of ultracold molecules as a platform for quantum computation.

arXiv comment19 pages, 12 figures

References in corpus (51)

• Advances in Quantum Metrology
• Quantum Computing
• A Unified Approach to the Classical Statistical Analysis of Small Signals
• Quantum Simulation
• Quantum Coherence as a Resource
• Search for New Physics with Atoms and Molecules
• Quantum computation with trapped polar molecules
• Cold and Ultracold Molecules: Science, Technology, and Applications
• A toolbox for lattice spin models with polar molecules
• Quantum Thermodynamics
• Realizing a lattice spin model with polar molecules
• Quantum Thermodynamics
• Cold molecules: Progress in Quantum Engineering of Chemistry and Quantum Matter
• Creation of ultracold ${}^{87}$RbCs molecules in the rovibrational ground state
• Single ion-qubit exceeding one hour coherence time
• Schemes for robust quantum computation with polar molecules
• An Optical Tweezer Array of Ultracold Molecules
• Precision Test of Mass Ratio Variations with Lattice-Confined Ultracold Molecules
• Quantum magnetism with multicomponent polar molecules in an optical lattice
• Dipolar Exchange Quantum Logic Gate with Polar Molecules
• Quantum Magnetism with Polar Alkali Dimers
• Suppressing the loss of ultracold molecules via the continuous quantum Zeno effect
• Ultracold polar molecules as qudits
• Second-Scale Nuclear Spin Coherence Time of Trapped Ultracold ${}^{23}$Na${}^{40}$K Molecules
• The hyperfine energy levels of alkali metal dimers: ground-state polar molecules in electric and magnetic fields
• Assembly of a rovibrational ground state molecule in an optical tweezer
• Topological phases in ultracold polar-molecule quantum magnets
• Collisions of ultracold ^{23}Na^{87}Rb molecules with controlled chemical reactivities
• Sticky collisions of ultracold RbCs molecules
• Observation of Collisions between Two Ultracold Ground-State CaF Molecules
• Loss of ultracold RbCs molecules via optical excitation of long-lived two-body collision complexes
• Anisotropic Polarizability of Ultracold Polar ${}^{40}$K${}^{87}$Rb Molecules
• A robust entangling gate for polar molecules using magnetic and microwave fields
• State-to-state control of ultracold molecular reactions
• Coherent Microwave Control of Ultracold ${}^{23}$Na${}^{40}$K Molecules
• Forming a single molecule by magnetoassociation in an optical tweezer
• Synthetic dimensions in ultracold molecules: quantum strings and membranes
• Extending rotational coherence of interacting polar molecules in a spin-decoupled magic trap
• Production of optically trapped ${}^{87}$RbCs Feshbach molecules
• Controlling the Rotational and Hyperfine State of Ultracold ${}^{87}$Rb${}^{133}$Cs Molecules
• Electric field-dependent dynamic polarizability and "magic" conditions for optical trapping of polar molecules
• Hyperfine structure of alkali-metal diatomic molecules
• Tune-out and magic wavelengths for ground-state ${}^{23}$Na${}^{40}$K molecules
• AC Stark Effect in Ultracold Polar RbCs Molecules
• A Simple, Versatile Laser System for the Creation of Ultracold Ground State Molecules
• Unified model of ultracold molecular collisions
• Controlling the ac Stark effect of RbCs with dc electric and magnetic fields
• Preparation of one ${}^{87}$Rb and one ${}^{133}$Cs atom in a single optical tweezer
• Strings of ultracold molecules in a synthetic dimension
• Magic Conditions for Multiple Rotational States of Bialkali Molecules in Optical Lattices
• Coherent Manipulation of the Internal State of Ultracold ${}^{87}$Rb${}^{133}$Cs Molecules with Multiple Microwave Fields

Cited by in corpus (2)

• Theoretical Aspects of Radium-Containing Molecules Amenable to Assembly from Laser-Cooled Atoms for New Physics Searches
• Characterization of the lowest excited-state ro-vibrational level of ${}^{23}$Na${}^{87}$Rb