Nanophotonic Quantum Storage at Telecommunication Wavelength

Ioana Craiciu, Mi Lei, Jake Rochman, Jonathan M. Kindem, John G. Bartholomew, Evan Miyazono, Tian Zhong, Neil Sinclair, and Andrei Faraon

Phys. Rev. Applied 12, 024062 – Published 30 August 2019

Abstract

Quantum memories for light are important components for future long-distance quantum networks. We present on-chip quantum storage of telecommunication-band light at the single-photon level in an ensemble of erbium-167 ions in an yttrium orthosilicate photonic crystal nanobeam resonator. Storage times of up to $10 μ s$ are demonstrated with an all-optical atomic-frequency-comb protocol in a dilution refrigerator under a magnetic field of 380 mT. We show this quantum-storage platform to have high bandwidth, high fidelity, and multimode capacity, and we outline a path toward an efficient erbium-167 quantum memory for light.

Received 15 January 2019
Revised 24 June 2019

DOI:https://doi.org/10.1103/PhysRevApplied.12.024062

Physics Subject Headings (PhySH)

Cavity quantum electrodynamics Nanophotonics Optical fibers Quantum communication Quantum memories

Communication networks Diode lasers Rare-earth doped crystals

Atomic, Molecular & Optical

Authors & Affiliations

Ioana Craiciu ^1,2, Mi Lei^1,2, Jake Rochman^1,2, Jonathan M. Kindem^1,2, John G. Bartholomew^1,2, Evan Miyazono^1,2, Tian Zhong^1,2,†, Neil Sinclair^3,4, and Andrei Faraon^1,2,*

¹Kavli Nanoscience Institute and Thomas J. Watson, Sr., Laboratories of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA
²Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
³Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, California 91125, USA
⁴Alliance for Quantum Technologies, California Institute of Technology, Pasadena, California 91125, USA

^*faraon@caltech.edu
^†Present address: Institute of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 12, Iss. 2 — August 2019

Subject Areas

Reuse & Permissions

Access Options

Article Available via CHORUS

Download Accepted Manuscript

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Finite-element-analysis simulation of the TM cavity mode in the triangular nanobeam resonator. The red-blue color gradient indicates the electric field component normal to the surface, $E_{z}$ ; the black outline indicates the YSO-air interface; a yellow arrow indicates coupling. (b) Scanning electron micrograph of the resonator, showing input and output coupling through a $45^{\circ}$ slot coupler. (c) Experimental setup (details are given in the main text). (d) Energy diagram of ${}^{167}{Er}^{3 +}$ :YSO, showing the $^{4} I_{15 / 2} \to^{4} I_{13 / 2}$ optical transition for crystallographic site 2. (e) Reflection spectrum of the cavity when tuned on resonance to the 1539-nm ${}^{167}{Er}^{3 +}$ :YSO transition. Detuning is measured from $194 816 \pm 2 GHz$ . The inset shows a close up of ion coupling before (black) and after (red) partial hyperfine initialization. The circles are data points, and solid black and dashed red lines are fits to theory (see the main text for details). AOM, acousto-optic modulator; EOM, electro-optic phase modulator; MEMS, microelectromechanical switch; ND, neutual density; SNSPD, superconducting-nanowire single-photon detector.
Reuse & Permissions
Figure 2
AFC experiment in the nanobeam cavity. (a) A section of the resonator reflection spectrum, showing an atomic frequency comb in the center of the inhomogeneously broadened ${}^{167}{Er}^{3 +}$ transition. Detuning is measured from $194 814.2 \pm 0.1 GHz$ . The apparent slope of the comb is due to its center frequency not being precisely aligned to the cavity resonance, leading to a dispersive shape. (b) AFC pulse sequence showing amplitude (yellow) and frequency (purple) modulation of the laser (pulses not to scale, see the main text for detail). (c) AFC storage: the input pulse (dashed red line) is partially absorbed by the comb; an output pulse is emitted at time $t = 1 / Δ = 165 ns$ (black line, $\times 100$ ). The black line also shows the partially reflected input pulse ( $t = 0$ ) and a smaller second output pulse at $t = 330 ns$ .
Reuse & Permissions
Figure 3
AFC storage for $10 μ s$ in the nanobeam resonator. The dashed red line shows the input pulse. The black line shows the partially reflected input pulse and the output pulse $(\times 20 000)$ . The reflected input pulse appears small due to detector saturation. The inset shows a schematic of the pulse sequence following hyperfine initialization. Pairs of comb-preparation pulses $10 μ s$ apart are repeated $n_{pump} = 10 000$ times, followed by input pulses $20 ns$ wide, repeated $n_{input} = 10$ times.
Reuse & Permissions
Figure 4
Multimode and coherent storage in the nanobeam resonator. (a) Storage of multiple temporal modes: ten 20-ns-wide input pulses (reflection off cavity shown) and the corresponding ten output pulses $(\times 1000)$ from a 500-kHz AFC. (b) Visbility curve acquired in a double-comb experiment, with $Δ_{1} = 5.2$ MHz, $Δ_{2} = 3.4$ MHz, and $δ_{1} = 0$ MHz. The detuning of the second comb is swept from $δ_{2} = - 0.2$ MHz to $δ_{2} = 2.2$ MHz, and the intensity of the two central overlapping output pulses is measured. Black circles show the sum of counts in the overlapping pulse region with $\sqrt{N_{counts}}$ uncertainty bars. The red line shows a least-squares fit to a sinusoid. The inset shows the four output pulses (middle two overlapping) in the case of maximally constructive (dashed black line) and maximally destructive (solid red line) interference.
Reuse & Permissions
Figure 5
(a) Photoluminescence (PL) from the nanobeam device as a function of detuning at three refrigerator temperatures: 720 mK (gray squares), 385 mK (black diamonds), and 37 mK (red circles). Detuning is measured from $194 810 \pm 0.1$ GHz. PL is collected after a 500- $μ s$ resonant pulse at 0.3 pW (estimated power in the nanobeam). Background counts are subtracted, and each curve is normalized and offset for clarity. Solid lines are fits to a sum of two Gaussians with equal widths and center frequencies 3.2 GHz apart. The $| ↓ ⟩$ transition is at the higher frequency. (b) Electron spin temperatures (EST) computed from the PL data in (a) as a function of refrigerator temperature. The dashed gray line indicates where the two temperatures are equal. The inset shows an enlargement of the EST measurement at 37 mK (black circle) and the EST estimated during the $T_{2}$ measurement (green diamond) and the 165-ns storage experiment (blue square). To estimate the latter two temperatures, the same pattern of laser pulses as in the actual experiments is sent to the nanobeam, at 0.3 and 0.02 nW, respectively, and PL is collected after the pulses. Error bars are propagated standard deviations from photon counting ( $\sqrt{N_{counts}}$ ). In all measurements the laser frequency is slowly modulated within each transition to prevent hyperfine hole burning.
Reuse & Permissions

Physical Review Applied