A quantum network of entangled optical atomic clocks

Abstract

Optical atomic clocks are our most precise tools to measure time and frequency. They enable precision frequency comparisons between atoms in separate locations to probe the space-time variation of fundamental constants, the properties of dark matter, and for geodesy. Measurements on independent systems are limited by the standard quantum limit (SQL); measurements on entangled systems, in contrast, can surpass the SQL to reach the ultimate precision allowed by quantum theory - the so-called Heisenberg limit. While local entangling operations have been used to demonstrate this enhancement at microscopic distances, frequency comparisons between remote atomic clocks require rapid high-fidelity entanglement between separate systems that have no intrinsic interactions. We demonstrate the first quantum network of entangled optical clocks using two ${}^{88}$Sr${}^{+}$ ions separated by a macroscopic distance (2 m), that are entangled using a photonic link. We characterise the entanglement enhancement for frequency comparisons between the ions. We find that entanglement reduces the measurement uncertainty by a factor close to $\sqrt{2}$, as predicted for the Heisenberg limit, thus halving the number of measurements required to reach a given precision. Practically, today's optical clocks are typically limited by laser dephasing; in this regime, we find that using entangled clocks confers an even greater benefit, yielding a factor 4 reduction in the number of measurements compared to conventional correlation spectroscopy techniques. As a proof of principle, we demonstrate this enhancement for measuring a frequency shift applied to one of the clocks. Our results show that quantum networks have now attained sufficient maturity for enhanced metrology. This two-node network could be extended to additional nodes, to other species of trapped particles, or to larger entangled systems via local operations.

References in corpus (33)

• Quantum Cryptography
• The Quantum Internet
• Quantum sensing
• Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
• Quantum metrology
• Quantum metrology with nonclassical states of atomic ensembles
• Search for New Physics with Atoms and Molecules
• A quantum network of clocks
• Atomic clock performance beyond the geodetic limit
• An ${}^{27}$Al${}^{+}$ quantum-logic clock with systematic uncertainty below $10^{-18}$
• Large Scale Modular Quantum Computer Architecture with Atomic Memory and Photonic Interconnects
• Hunting for topological dark matter with atomic clocks
• Optical clock intercomparison with $6\times 10^{-19}$ precision in one hour
• 'Designer atoms' for quantum metrology
• Entanglement-Enhanced Optical Atomic Clock
• High-rate, high-fidelity entanglement of qubits across an elementary quantum network
• Atomic Clocks for Geodesy
• Quantum-enhanced sensing of displacements and electric fields with large trapped-ion crystals
• Improved limits for violations of local position invariance from atomic clock comparisons
• Imaging optical frequencies with 100 $\mu$Hz precision and 1.1 $\mu$m resolution
• A long-lived Zeeman trapped-ion qubit
• Motional Fock states for quantum-enhanced amplitude and phase measurements with trapped ions
• Precision measurement of atomic isotope shifts using a two-isotope entangled state
• Precision spectroscopy with two correlated atoms
• Benchmarking a high-fidelity mixed-species entangling gate
• Probing beyond the laser coherence time in optical clock comparisons
• Lifetime-Limited Interrogation of Two Independent ${}^{27}{\text{Al}}^{+}$ Clocks Using Correlation Spectroscopy
• On-Line Estimation of Local Oscillator Noise and Optimisation of Servo Parameters in Atomic Clocks
• Improved Test of Local Lorentz Invariance from a Deterministic Preparation of Entangled States
• Robust optical clock transitions in trapped ions
• A tweezer clock with half-minute atomic coherence at optical frequencies and high relative stability
• A two-way photonic interface for linking Sr+ transition at 422 nm to the telecommunications C-band
• Optical coherence between atomic species at the second scale: improved clock comparisons via differential spectroscopy

Cited by in corpus (38)

• Entanglement of Nanophotonic Quantum Memory Nodes in a Telecom Network
• Entanglement of trapped-ion qubits separated by 230 meters
• Distributed quantum sensing with a mode-entangled network of spin-squeezed atomic states
• Quantum networks with neutral atom processing nodes
• A telecom-wavelength quantum repeater node based on a trapped-ion processor
• Multi-qubit gates and Schrödinger cat states in an optical clock
• Entanglement-enhanced quantum metrology: from standard quantum limit to Heisenberg limit
• Robust Quantum Memory in a Trapped-Ion Quantum Network Node
• Development of a Boston-area 50-km fiber quantum network testbed
• Multi-site Integrated Optical Addressing of Trapped Ions
• Entanglement-Enhanced Optical Atomic Clocks
• Active cancellation of servo-induced noise on stabilized lasers via feedforward
• Fast photon-mediated entanglement of continuously-cooled trapped ions for quantum networking
• Manipulating growth and propagation of correlations in dipolar multilayers: From pair production to bosonic Kitaev models
• Parallelized telecom quantum networking with a ytterbium-171 atom array
• Private and Robust States for Distributed Quantum Sensing
• Atomic clock locking with Bayesian quantum parameter estimation: scheme and experiment
• Demonstration of chronometric leveling using transportable optical clocks beyond laser coherence limit
• Realization of a crosstalk-free two-ion node for long-distance quantum networking
• Testing quantum theory on curved space-time with quantum networks
• Quadrupole transitions and quantum gates protected by continuous dynamic decoupling
• Probing curved spacetime with a distributed atomic processor clock
• An optical atomic clock using $4D_J$ states of rubidium
• Robust atom-photon gate for quantum information processing
• Achieving Heisenberg scaling by probe-ancilla interaction in quantum metrology
• Nonlocal phase modulation of multimode, continuous-variable twin beams
• Entanglement-enhanced Synchronous differential comparison
• Indefinite Time Directed Quantum Metrology
• Protocol for suppression of noise from stimulated multi-photon emissions in concatenated entanglement swapping links and quantum repeaters
• Quantum-private distributed sensing
• Kilometer-Scale Ion-Photon Entanglement with a Metastable ${}^{88}$Sr${}^{+}$ Qubit
• Temporally multiplexed ion-photon quantum interface via fast ion-chain transport
• Compatibility of trapped ions and dielectrics at cryogenic temperatures
• Optimal quantum precision in noise estimation: Is entanglement necessary?
• Multiplexed ion-ion entanglement over $1.2$ kilometer fibers
• Non canonical polarizations of Gravitational Waves
• From Independent to Joint: Enhancing Quantum Phase and Correlation Factor Estimation by Squeezed Reservoir Engineering
• Global-scale quantum networking using hybrid-channel quantum repeaters with relays based on a chain of balloons