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Single Rare-Earth Ions in Solid-State Hosts: A Platform for Quantum Networks


Ruskuc, Andrei (2024) Single Rare-Earth Ions in Solid-State Hosts: A Platform for Quantum Networks. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ecn2-pp53.


Solid-state defects have emerged as leading candidates for quantum network nodes due to their compatibility with scalable device engineering and local nuclear spins for quantum processing. Rare-earth ions in crystalline hosts are particularly attractive due to their long optical and spin coherence times at cryogenic temperatures. However, until recently, detection and utilization of single rare-earth ions in quantum technologies has been hindered by their inherently weak optical transitions. In this thesis I present progress towards realizing a novel quantum network node architecture using single ¹7¹Yb³⁺ ions in YVO₄, coupled to a nanophotonic cavity.

First, we demonstrate coherent operation of single ¹7¹Yb³⁺ ions as optically addressed qubits. To do this, we leverage first order insensitivity of optical and spin transitions to electric and magnetic fields, thereby protecting the qubits from environmental noise. We demonstrate initialization, high fidelity control and readout of a hyperfine spin qubit with long quantum storage times. We also characterize the optical transitions and find a lifetime-limited echo coherence, thereby enabling a coherent spin-photon interface.

Next, we focus on realizing an auxiliary quantum register. The high-fidelity spin control of our ¹7¹Yb³⁺ qubit is leveraged to access local nuclear spins. These spins comprise a dense ensemble which serves as a deterministic quantum resource. We utilize Hamiltonian engineering to generate tailored interactions, enabling polarization, coherent control and preparation of many-body nuclear spin states. Finally, we implement a spin-wave based memory protocol and demonstrate storage and retrieval of quantum states.

Moving beyond a single quantum node, in the final section of this thesis we will realize a small-scale quantum network using this platform. As a first step we demonstrate time-resolved quantum interference between photons emitted by ions in two separate devices. Then, we demonstrate a novel heralded entanglement protocol which incorporates optical dynamical decoupling and frequency erasure via precise photon detection. This protocol counteracts both static and dynamic inhomogeneity in the ions’ optical transition frequencies, thereby enabling entanglement generation between any pair of qubits in a scalable fashion.

These results showcase single rare-earth ions as a promising platform for the future quantum internet.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:rare-earth ions; nanophotonic resonator; cavity quantum electrodynamics; quantum networks; nuclear spins; quantum light-matter interfaces; remote entanglement
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Faraon, Andrei
Group:Institute for Quantum Information and Matter, Kavli Nanoscience Institute
Thesis Committee:
  • Endres, Manuel A. (chair)
  • Faraon, Andrei
  • Painter, Oskar J.
  • Hutzler, Nicholas R.
Defense Date:21 September 2023
Non-Caltech Author Email:andreiruskuc (AT)
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-18-1-0374
Air Force Office of Scientific Research (AFOSR)FA9550-21-1-0055
National Science Foundation2210570
National Science Foundation1820790
Institute of Quantum Information and Matter, an NSF Physics Frontiers Center, with support from the Moore FoundationPHY-1733907
Record Number:CaltechTHESIS:10202023-123922325
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 3. adapted for Chapters 4, 5, 6.
Ruskuc, Andrei0000-0001-7684-7409
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16211
Deposited By: Andrei Ruskuc
Deposited On:20 Oct 2023 23:26
Last Modified:20 Oct 2023 23:26

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