Frequency-encoded photonic qubits for scalable quantum information processing

Abstract

Among the objectives toward large-scale quantum computation is the quantum interconnect: a device which uses photons to interface qubits that otherwise could not interact. However, current approaches require photons indistinguishable in frequency-a major challenge for systems experiencing different local environments or of different physical compositions altogether. Here we develop an entirely new platform which actually exploits such frequency mismatch for processing quantum information. Labeled "spectral linear optical quantum computation" (spectral LOQC), our protocol offers favorable linear scaling of optical resources and enjoys an unprecedented degree of parallelism, as an arbitrary N -qubit quantum gate may be performed in parallel on multiple N -qubit sets in the same linear optical device. Not only does spectral LOQC offer new potential for optical interconnects; it also brings the ubiquitous technology of high-speed fiber optics to bear on photonic quantum information, making wavelength-configurable and robust optical quantum systems within reach.

50-GHz-spaced comb of high-dimensional frequency-bin entangled photons from an on-chip silicon nitride microresonator

“…With parallel detection with a sufficient number of detectors, multiple sidebands lying between original biphoton comb lines could be used, substantially mitigating unnecessary loss and opening the door to stronger phase modulation to construct superpositions of a larger number of frequency bins. Tailoring the rf waveform driving the phase modulator could also contribute to improving efficiency [27].…”

Electro-Optic Frequency Beam Splitters and Tritters for High-Fidelity Photonic Quantum Information Processing

“…For example, optical filters and/or low temperatures are required to remove background noise due to powerful optical pumps, either from the sources themselves or Raman scattering in the nonlinear medium. And achieving the necessary nonlinear mixing for arbitrary combinations of modes will require additional pump fields, as well as properly engineered phase-matching conditions.Recently we proposed a fundamentally distinct platform for frequency-bin manipulations, relying on electrooptic phase modulation and Fourier-transform pulse shaping for universal QIP [12]. Our approach requires no optical pump fields, is readily parallelized, and scales well with the number of modes.…”

“…Combined with its native parallelizability and absence of optical noise sources, our mixer design offers new opportunities for a range of quantum information applications, including linearoptical computation [12], quantum repeaters [13], and quantum walks [14]. The tritter also serves as an elementary building block for a frequency version of three-mode directionally unbiased linear-optical multiports, which find application in quantum simulations [15] and Bell state discriminators [16].Background.-The Hilbert space of interest consists of a comb of equispaced frequency bins, with operatorsâ n (n ∈ Z) that annihilate a single photon in the narrowband modes centered at frequencies ω n = ω 0 + n∆ω [12,17]. A qudit is represented by a single photon spread over d such modes, and the objective is to implement a frequency multiport V connecting the inputâ (in) n and outputâ (out) m modes in some desired fashion:â…”

Generation of frequency sidebands on single photons with indistinguishability from quantum dots

“…As the modulator is embedded in a single-mode fiber, all of the frequency components are in the same spatial mode. This allows transferring such qubit states over a long distance using fiber optic networks without the problems that characterize polarization qubits [14]. Through HOM measurements, we have demonstrated that the indistinguishability of a stream of individual photons emitted by a QD is fully preserved in the presence of additional frequency sidebands generated via a phase modulator for a range of modulation frequencies.…”

“…Frequency qubits can be generated through phase modulation of a single photon [14,16], where the information is encoded in the relative amplitude between the sidebands. Recently, Lukens and Lougovski proposed a universal linearoptical quantum computing (LOQC) platform using frequency components generated from an electro-optic modulators [14]. Similarly, there has been proof-of-concept demonstrations of the 1984 protocol of Bennett and Brassard (BB84) using phase-modulated weak coherent sources [13,17].…”