Abstract
The quantum frequency processor (QFP) enables universal quantum gates, but demonstrations so far have employed discrete components only. We introduce a QFP model for microring resonator-based pulse shapers, analyzing Hadamard gates as examples. Extendable to any material, our model furnishes valuable tools for integrated QFPs.
| Original language | English |
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| Title of host publication | 2022 IEEE Photonics Conference, IPC 2022 - Proceedings |
| Publisher | Institute of Electrical and Electronics Engineers Inc. |
| ISBN (Electronic) | 9781665434874 |
| DOIs | |
| State | Published - 2022 |
| Event | 2022 IEEE Photonics Conference, IPC 2022 - Vancouver, Canada Duration: Nov 13 2022 → Nov 17 2022 |
Publication series
| Name | 2022 IEEE Photonics Conference, IPC 2022 - Proceedings |
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Conference
| Conference | 2022 IEEE Photonics Conference, IPC 2022 |
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| Country/Territory | Canada |
| City | Vancouver |
| Period | 11/13/22 → 11/17/22 |
Funding
This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). logical qubit, plus two on either side as vacuum ancillas. Accordingly, we allocate M = 6 (M = 12) channels for a single (two parallel) Hadamard operations. Assuming operation in silicon at 300 K, 480 nm × 220 nm waveguide cross-section, 0.5 dB/cm attenuation, and TE polarization, we design ring radii r ≈ 20 µm and take symmetric coupling constants of 0.01 (in power) for each MRR; 2πω0 = 193 THz and 2π∆ω = 15 GHz define the nominal frequency mode space ωm used by the pulse shaper. As shown in Fig. 1(b), the pulse shaper response varies strongly both within and across the 15 GHz-wide bins, which emphasizes the need to define fidelity F(Ω) and success probability P(Ω) with respect to the ideal unitary [1] as a function of frequency offset Ω from the peak, i.e., separately for each family of comblines defined as ω˜m = ωm + Ω. Intuitively, this definition recognizes that frequency bins experience different global operations depending on their spectral position relative to the MRR peaks. Consequently, after incorporating the mixing operations from two bookend EOMs—assumed ideal for this study (linear with negligible voltage-dependent loss)—we find the offset-dependent F(Ω) and P(Ω) in Fig. 2(a) (the latter normalized to a peak of 0.73, due to a combination of MRR insertion loss and scattering into adjacent frequency modes). The fidelity remains above 0.9998 in both scenarios, even at a |Ω| = 2 GHz; the success probability is halved with |Ω| = 0.6 GHz. PIC-based pulse shapers also provide opportunities for much tighter bin spacings through the distinctive behavior encapsulated in Eq. (1). Here we repeat the previous analyses for a fixed offset Ω = 0 but variable ∆ω [shown in Fig. 2(b)]. Apart from a sharp drop for the parallel case at 2π∆ω ≈ 49 GHz, which can be attributed to crosstalk from overlapping resonances one free spectral range away [4], both F and P generally decrease with smaller ∆ω. Significantly, F > 0.999 and P > 0.50 down to spacings as small as 1.85 GHz, well below the ∼18 GHz practical minimum observed so far for table-top QFPs [11]. And with high-order MRR filters, even sub-GHz separations appear feasible with current technology [4]. Such integrated QFPs can facilitate high-dimensional frequency mixers [13]—which can be implemented on a three-element QFP with additional RF tones (i.e., integer multiples of ∆ω)—and furnish new opportunities in quantum communications and networking based on frequency-bin qudits. We thank A. M. Weiner and K. V. Myilswamy for valuable discussions. This research was performed in part at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract no. DE-AC05-00OR22725. Funding was provided by the U.S. Department of Energy, Office of Science, through the SULI and Early Career Research Programs (ERKJ353); and AFRL Prime Order No. FA8750-20-P-1705. References 1. J. M. Lukens and P. 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