Quantum Nano-Photonic Devices

Updated March 2023

Our group develops quantum nano-photonic devices based on luminescent centers in solids - also known as optical defects, or artificial atoms. Currently we mainly work with rare-earths doped in crystals, and actively explore other systems like luminescent centers in silicon and 2D materials.

Rare-earth-doped materials

Rare earth ions (Lanthanides) doped in crystals have excellent optical (millisecond for Erbium in yttrium orthosilicate or YSO) and electron/nuclear spin coherence (up to 6 hours demonstrated in europium doped YSO). Rare-earth doped materials are quite commonly used in optics, like in solid state and fiber lasers, and more recently in optical quantum memories. We are developing nano-photonic devices in rare-earth doped crystals that will lead to highly coherent optical quantum bits, optical quantum memories and devices for efficient quantum conversion between optical photons and microwave photons. These technologies will be used in future optical quantum networks for distributing entanglement over long distances. Applications include secure communications, interconnecting and parallelizing future quantum computers, and tests of fundamental physics.

Single optically addressable quantum bits based on rare-earths are currently being developed in our group. By embedding the rare-earths in nano-photonic cavities, their emission rates become fast and close to Fourier transform limited. We are currently mainly focusing on ytterbium-171 in yttrium orthovanadate. This atom has the simplest hyperfine level structure that can be used to achieve spin transitions with long coherence times. We demonstrated that this is a reliable optically addressable quantum bit with long coherence time (tens of milliseconds). It also has access to a local quantum memory register formed of a localized ensemble of vanadium nuclear spins. Current efforts are in developing optical quantum networks using this system and on investigating interesting quantum many body physics using the ytterbium qubit that can couple to various nuclear and electronic spins in the crystal.

Relevant publications:

1. Andrei Ruskuc, Chun-Ju Wu, Jake Rochman, Joonhee Choi, Andrei Faraon, Nuclear spin-wave quantum register for a solid-state qubit, Nature, 602, 408–413 (2022). Open Access Version, ArXiv Version. See highlights in Nature Physics News and Views. Thank you Claire Le Gall!
2. Jonathan M. Kindem, Andrei Ruskuc, John G. Bartholomew, Jake Rochman, Yan Qi Huan, Andrei Faraon, Coherent control and single-shot readout of a rare-earth ion embedded in a nanophotonic cavity, Nature, 580, 201–204 (2020). Open Access Version, ArXiv Version. See highlights in Nature Physics News and Views. Thank you Roman Kolesov & Jörg Wrachtrup! Also, check out Caltech News.
3. Tian Zhong, Jonathan M. Kindem, John G. Bartholomew, Jake Rochman, Ioana Craiciu, Varun Verma, Sae Woo Nam, Francesco Marsili, Matthew D. Shaw, Andrew D. Beyer, Andrei Faraon, Optically addressing single rare-earth ions in a nanophotonic cavity, Physical Review Letters , Vol. 121, 183603 (2018), ArXiv Version

Other selected publications:

1. Tian Xie, Jake Rochman, John G. Bartholomew, Andrei Ruskuc, Jonathan M. Kindem, Ioana Craiciu, Charles Thiel, Rufus Cone, Andrei Faraon, Characterization of Er3+:YVO4 for microwave to optical transduction, Physical Review B, 104, 054111, 2021, ArXiv Version
2. John G. Bartholomew, Tian Zhong, Jonathan M. Kindem, Raymond Lopez-Rios, Jake Rochman, Ioana Craiciu, Evan Miyazono, Andrei Faraon, Controlling rare-earth ions in a nanophotonic resonator using the ac Stark shift, Physical Review A , 97, 063854, 2018, ArXiv Version
3. Evan Miyazono, Ioana Craiciu, Amir Arbabi, Tian Zhong, Andrei Faraon, Coupling erbium dopants in yttrium orthosilicate to silicon photonic resonators and waveguides, Optics Express Vol. 25, Issue 3, pp. 2863-2871 (2017), [https://doi.org/10.1364/OE.25.002863]
4. Tian Zhong, Jonathan M. Kindem, Jake Rochman, Andrei Faraon, Interfacing broadband photonic qubits to on-chip cavity-protected rare-earth ensembles, Nature Communications, 8, Article number: 14107 (2017), [DOI: 10.1038/ncomms14107], (arXiv:1604.00143)
5. Evan Miyazono, Tian Zhong, Ioana Craiciu, Jonathan M Kindem, Andrei Faraon, Coupling of erbium dopants to yttrium orthosilicate photonic crystal cavities for on-chip optical quantum memories, Applied Physics Letters 108, 011111 (2016), [doi: http://dx.doi.org/10.1063/1.4939651], arXiv:1512.07389
6. Tian Zhong, Jonathan M. Kindem, Evan Miyazono, Andrei Faraon, Nanophotonic coherent light-matter interfaces based on rare-earth-doped crystals, Nature Communications 6, Article number: 8206, (2015),[], ArXiv , arXiv:1507.00977 [quant-ph]

Optical quantum memories can be implemented with ensemble of rare-earth ions doped in various materials. Photons can be stored directly into optical transitions using atomic frequency comb protocols or controlled reversible inhomogeneous broadening, with storage times ultimately limited by the optical coherence time. Longer memory times can be achieved by transferring the coherence onto a superposition of electron spin or nuclear spin states (spin-wave).

Our group works on on-chip optical quantum memories based on rare-earth-doped crystals. To achieve high efficiencies on a chip it is important to embed the rare-earth atoms in nano-photonic resonators that enhance the coupling between photons and small ensemble of atoms. The materials that we use are based on neodymium and erbium. We already demonstrated memories based on the atomic frequency comb protocol using neodymium and erbium ensembles. The next step is to extend the memory time by pursuing spin-wave protocols. We are also actively working on integrating these memories with silicon photonics and on-chip electrodes. The electrical control will enable us to control when the light is emitted, and also the bandwidth and frequency of the emitted photons which are examples of on-chip linear optical processing at single photon level.

Relevant Publications:

1. Ioana Craiciu, Mi Lei, Jake Rochman, John G. Bartholomew, Andrei Faraon, Multifunctional on-chip storage at telecommunication wavelength for quantum networks, Optica, Vol. 8, Issue 1, pp. 114-121 (2021), [https://doi.org/10.1364/OPTICA.412211], ArXiv Version.
2. Ioana Craiciu, Mi Lei, Jake Rochman, Jonathan M. Kindem, John G. Bartholomew, Evan Miyazono, Tian Zhong, Neil Sinclair, Andrei Faraon, Nanophotonic quantum storage at telecommunications wavelength, Physical Review Applied, 12, 024062, 2019, ArXiv Version
3. Tian Zhong, Jonathan M. Kindem, John G. Bartholomew, Jake Rochman, Ioana Craiciu, Varun Verma, Sae Woo Nam, Francesco Marsili, Matthew D. Shaw, Andrew D. Beyer, Andrei Faraon, Optically addressing single rare-earth ions in a nanophotonic cavity, Physical Review Letters , Vol. 121, 183603 (2018), ArXiv Version

Quantum transduction between microwave (~5GHz) photons and optical photons will enable quantum communications between future superconducting quantum computers. Rare-earth ions exhibit transitions both in the optical domain and in microwave domain, and thus can serve as a quantum transduction medium. To enable efficient transduction, the rare-earths must be coupled to both optical and microwave resonators. We develop optical to microwave quantum transductors based on rare-earths (¹⁷⁰Er and ¹⁷¹Yb) coupled to nano-photonic and superconducting microwave resonators. The experiments are done in dilution refrigerators.

Relevant Publications:

1. John G. Bartholomew, Jake Rochman, Tian Xie, Jonathan M. Kindem, Andrei Ruskuc, Ioana Craiciu, Mi Lei, Andrei Faraon, On-chip coherent microwave-to-optical transduction mediated by ytterbium in YVO₄, Nature Communications, 11, Article 3266 (2020), ArXiv Version (2019)

Other materials

We are constantly exploring other material systems with interesting optically addressable spins. Currently we have efforts on luminescent spin centers in silicon and 2D materials.