Photon-Photon Quantum Phase Gate in a Photonic Molecule with ${\ensuremath{\chi}}^{(2)}$ Nonlinearity

Editors' Suggestion

Photon-Photon Quantum Phase Gate in a Photonic Molecule with $χ^{(2)}$ Nonlinearity

Ming Li, Yan-Lei Zhang, Hong X. Tang, Chun-Hua Dong, Guang-Can Guo, and Chang-Ling Zou

Phys. Rev. Applied 13, 044013 – Published 6 April 2020

Abstract

The construction of a photon-photon quantum phase gate based on photonic nonlinearity has long been a fundamental issue, and is vital for deterministic and scalable photonic quantum-information processing. It requires not only strong nonlinear interaction at the single-photon level but also suppressed phase noise and spectral entanglement for high gate fidelity. In this paper, we propose that a high-quality-factor microcavity with strong $χ^{(2)}$ nonlinearity can be quantized to anharmonic energy levels and can be effectively treated as an artificial atom. Such an artificial atom has a size much larger than the photon wavelength, which enables passive and active ultrastrong coupling to traveling photons. A high-fidelity quantum control phase gate is realized by our mediating the phase between photons with an intermediate artificial atom in a photonic molecule structure. The scheme avoids two-photon emission and thus eliminates spectral entanglement and quantum phase noise. Experimental realization of the artificial atom can be envisioned on an integrated photonic chip and holds great potential for single-emitter-free, room-temperature quantum-information processing.

Received 30 September 2019
Revised 2 March 2020
Accepted 23 March 2020

DOI:https://doi.org/10.1103/PhysRevApplied.13.044013

Physics Subject Headings (PhySH)

Integrated optics Kerr effect Nonlinear optics Optical quantum information processing Photonics Quantum gates Quantum optics with artificial atoms

Atomic, Molecular & OpticalQuantum Information, Science & Technology

Authors & Affiliations

Ming Li ^1,2, Yan-Lei Zhang^1,2, Hong X. Tang³, Chun-Hua Dong^1,2,*, Guang-Can Guo^1,2, and Chang-Ling Zou ^1,2,4,†

¹Key Laboratory of Quantum Information, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, 230026 Anhui, People’s Republic of China
²CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, 230026 Anhui, People’s Republic of China
³Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA
⁴National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093 Jiangsu, China

^*chunhua@ustc.edu.cn
^†clzou321@ustc.edu.cn

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 13, Iss. 4 — April 2020

Subject Areas

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Artificial atom based on an optical cavity with strong $χ^{(2)}$ nonlinearity. (a) Left: degenerate and nondegenerate three-wave mixing, corresponding to SHG and sum-frequency generation. Right: energy-level structures for $χ^{(2)}$ interaction. (b) Vacuum Rabi splitting of the populations of state $| 2_{a} 0_{c} ⟩$ for SHG. The black curve corresponds to $g_{d} / κ_{a} = 4$ and the red curve corresponds to $g_{d} / κ_{a} = 8$ . The driving strength $ε_{p} = 0.2$ . (c) Rabi oscillation of the single-photon-excitation state $| 1_{a} 0_{c} ⟩$ population under coherent driving. The black curve corresponds to $ε_{p} = 10$ and red curve corresponds to $ε_{p} = 20$ . The coupling strength $g_{d} / κ_{a} = 80$ . The cavity decay rates are set at $κ_{a} = κ_{c} = 1$ .
Reuse & Permissions
Figure 2
Coupling between a waveguide and an artificial atom made by a microring cavity. (a) The artificial atom is coupled with a waveguide with a wrapped-around structure. The coupling rate can be 3 orders of magnitude greater than the decay rate. (b) Dual-rail encoding scheme for a quantum gate of two propagating photons. The two photons are multiplexed into the same waveguide and interact with each other in the $χ^{(2)}$ medium and are then demultiplexed to different waveguides. A time delay is added in the first path to make $| 0 ⟩_{c}$ and $| 1 ⟩_{c}$ synchronized in the time domain. (c) Input state of a separable two-photon state with Gaussian shape $ϕ_{in} (k_{1}, k_{2}) = (1 / 2 π σ^{2}) \exp [- (k_{1}^{2} + k_{2}^{2}) / 2 σ^{2}]$ , where $k_{1}$ ( $k_{2}$ ) is the frequency of the photon and $σ = 0.5$ is the width of the frequency distribution. (d) Output state. The nonlinear coupling strength $g_{d} = 3$ and the decay rates of the second-harmonic mode $κ_{c, 0} = κ_{c, 1} = 1$ and the fundamental mode $κ_{a, 0} = 1$ , $κ_{a, 1} = 3$ , where $κ_{a, 0}$ ( $κ_{c, 0}$ ) is the intrinsic decay rate and $κ_{a, 1}$ ( $κ_{c, 1}$ ) is the external coupling rate to the waveguide. DEMUX, time-bin demultiplexer; MUX, time-bin multiplexer.
Reuse & Permissions
Figure 3
The photon-photon controlled-phase gate in a photonic molecule. (a) Schematic of a photonic molecule. The cavity coupled to the waveguide serves as an active antenna as shown in Fig. 2. (b) Time sequence of the EO drive for the quantum storage and retrieval of the photons. In the calculation, $κ_{d, 1} = 10^{3} κ_{d, 0}$ , $κ_{d, 0} = 2 κ$ , and the intrinsic decay rate of the artificial atom $κ_{a, 0} = κ_{b, 0} = κ = 1$ . The pulse shape of the control photon is a Gaussian function $a_{in}^{c} = α \{\exp [- 25 (t / T_{c} - 0.5) - \exp (- 6.25)]\}$ , and similarly for the target photon $b_{in}^{t}$ . $α$ is the normalization factor. The duration of the two photons is $T_{c} = T_{t} = 0.1 / κ$ . (c) Gate fidelity versus nonlinear coupling strength $g$ .
Reuse & Permissions

Physical Review Applied

Photon-Photon Quantum Phase Gate in a Photonic Molecule with χ(2) Nonlinearity

Ming Li, Yan-Lei Zhang, Hong X. Tang, Chun-Hua Dong, Guang-Can Guo, and Chang-Ling Zou

Phys. Rev. Applied 13, 044013 – Published 6 April 2020

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Subject Areas

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Photon-Photon Quantum Phase Gate in a Photonic Molecule with $χ^{(2)}$ Nonlinearity