# Hybrid quantum logic and a test of Bell’s inequality using two different atomic isotopes

@article{Ballance2015HybridQL, title={Hybrid quantum logic and a test of Bell’s inequality using two different atomic isotopes}, author={C. J. Ballance and V M Sch{\"a}fer and J. P. Home and D. J. Szwer and S. C. Webster and D. T. C. Allcock and Norbert Matthias Linke and T. Patrick Harty and Diana Prado Lopes Aude Craik and D. N. Stacey and Andrew M. Steane and D. M. Lucas}, journal={Nature}, year={2015}, volume={528}, pages={384-386} }

Entanglement is one of the most fundamental properties of quantum mechanics, and is the key resource for quantum information processing (QIP). Bipartite entangled states of identical particles have been generated and studied in several experiments, and post-selected or heralded entangled states involving pairs of photons, single photons and single atoms, or different nuclei in the solid state, have also been produced. Here we use a deterministic quantum logic gate to generate a ‘hybrid…

## 75 Citations

### Universal quantum gate with hybrid qubits in circuit quantum electrodynamics.

- PhysicsOptics letters
- 2018

The generality of this proposal allows implementing the proposed gate in a wide range of physical systems, such as two 1D or 3D microwave or optical cavities coupled to a natural or artificial three-level atom, and can be applied to create a novel entangled state between a particle-like photonic qubit and a wave-like cat-state qubit.

### Repeated multi-qubit readout and feedback with a mixed-species trapped-ion register

- Physics2019 Conference on Lasers and Electro-Optics (CLEO)
- 2019

Up to 50 sequential measurements of correlations between two beryllium ion microwave qubits using an ancillary optical qubit in a calcium ion are demonstrated, and feedback is implemented that allows us to stabilize two-qubit subspaces as well as Bell states, a class of maximally entangled states.

### Faithful conditional quantum state transfer between weakly coupled qubits

- PhysicsScientific reports
- 2016

This work proposes and experimentally demonstrates a procedure for faithful quantum state transfer between two weakly interacting qubits and enables a probabilistic yet perfect unidirectional transfer of an arbitrary unknown state of a source qubit onto a target qubit prepared initially in a known state.

### Multi-element logic gates for trapped-ion qubits

- PhysicsNature
- 2015

An entangling quantum gate between ions of different elements which can serve as an important building block of QIP, quantum networking, precision spectroscopy, metrology, and quantum simulation is demonstrated.

### Fast Gates and Mixed-Species Entanglement with Trapped Ions

- Physics
- 2020

Fast gates and mixed-species entanglement with trapped ions Vera M. Schäfer A thesis submitted for the degree of Doctor of Philosophy Hilary Term 2018 Balliol College, Oxford Building a quantum…

### Interference of Single Photons Emitted by Entangled Atoms in Free Space.

- PhysicsPhysical review letters
- 2018

This scheme, together with population measurements, provides a fully optical determination of the amount of entanglement and large sensitivity of the interference phase evolution points to applications of the presented scheme in high-precision gradient sensing.

### Photonic quantum state transfer between a cold atomic gas and a crystal

- PhysicsNature
- 2017

It is shown that a quantum state can be transferred faithfully between a cold atomic ensemble and a rare-earth-doped crystal by means of a single photon at 1,552 nanometre telecommunication wavelength, using cascaded quantum frequency conversion.

### Quantum control methods for robust entanglement of trapped ions

- PhysicsJournal of Physics B: Atomic, Molecular and Optical Physics
- 2022

A major obstacle in the way of practical quantum computing is achieving scalable and robust high-fidelity entangling gates. To this end, quantum control has become an essential tool, as it can make…

### Quantum information processing with mixed-species ion crystals

- Physics
- 2020

Trapped ions are among the leading platforms for the realization of scalable quantum information processing (QIP). A hybrid system composed of different species of ions extends the control…

### Single-site Rydberg addressing in 3D atomic arrays for quantum computing with neutral atoms

- PhysicsJournal of Physics B: Atomic, Molecular and Optical Physics
- 2020

Neutral atom arrays are particularly promising for large-scale quantum computing because it is possible to prepare large-scale qubit arrays. An unsolved issue is how to selectively excite one qubit…

## References

SHOWING 1-10 OF 57 REFERENCES

### High-fidelity two-qubit quantum logic gates using trapped calcium-43 ions

- Physics
- 2014

The generation of entanglement is a fundamental resource for quantum technology, and trapped ions are one of the most promising systems for storage and manipulation of quantum information. Here we…

### Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate

- PhysicsNature
- 2003

A universal geometric π-phase gate between two beryllium ion-qubits is demonstrated, based on coherent displacements induced by an optical dipole force, which makes it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ions.

### Multi-element logic gates for trapped-ion qubits

- PhysicsNature
- 2015

An entangling quantum gate between ions of different elements which can serve as an important building block of QIP, quantum networking, precision spectroscopy, metrology, and quantum simulation is demonstrated.

### Complete Methods Set for Scalable Ion Trap Quantum Information Processing

- PhysicsScience
- 2009

This work shows a combination of all of the fundamental elements required to perform scalable quantum computing through the use of qubits stored in the internal states of trapped atomic ions and quantified the repeatability of a multiple-qubit operation and observed no loss of performance despite qubit transport over macroscopic distances.

### Experimental Issues in Coherent Quantum-State Manipulation of Trapped Atomic Ions

- PhysicsJournal of research of the National Institute of Standards and Technology
- 1998

Some experimental issues in the proposal for trappedion quantum computation by J. I. Cirac and P. Zoller (University of Innsbruck) are discussed and several possible decoherence mechanisms are examined.

### Entangled states of trapped atomic ions

- PhysicsNature
- 2008

Experiments show that just a few entangled trapped ions can be used to improve the precision of measurements, and if the entanglement in such systems can be scaled up to larger numbers of ions, simulations that are intractable on a classical computer might become possible.

### High-Fidelity Quantum Logic Gates Using Trapped-Ion Hyperfine Qubits.

- PhysicsPhysical review letters
- 2016

We demonstrate laser-driven two-qubit and single-qubit logic gates with respective fidelities 99.9(1)% and 99.9934(3)%, significantly above the ≈99% minimum threshold level required for…

### Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres

- PhysicsNature
- 2015

The data imply statistically significant rejection of the local-realist null hypothesis and could be used for testing less-conventional theories, and for implementing device-independent quantum-secure communication and randomness certification.

### Bell inequality violation with two remote atomic qubits.

- PhysicsPhysical review letters
- 2008

We observe violation of a Bell inequality between the quantum states of two remote Yb+ ions separated by a distance of about 1 m with the detection loophole closed. The heralded entanglement of two…

### Scaling the Ion Trap Quantum Processor

- PhysicsScience
- 2013

The latest progress and prospects in the scaling of trapped ions to hundreds or thousands of qubits and beyond are reviewed, with the promise of advanced architectures and new technologies, such as microfabricated ion traps and integrated photonics.