Abstract:Quantum frequency conversion (QFC) of photonic signals preserves quantum information while simultaneously changing the signal wavelength. A common application of QFC is to translate the wavelength of a signal compatible with the current fiber-optic infrastructure to a shorter wavelength more compatible with high quality single-photon detectors and optical memories. Recent work has investigated the use of QFC to manipulate and measure specific temporal modes (TMs) through tailoring of the pump pulses. Such a sc… Show more
“…Important examples include the quantum pulse gate [2,3], which uses nonlinear mixing with shaped classical pulses for selective conversion of the time-frequency modes of single photons [4][5][6], and demonstrations of frequency beamsplitters based on both χ (2) [7,8] and χ (3) [9][10][11] nonlinearities, which interfere two wavelength modes analogously to a spatial beamsplitter. These seminal experiments have shown key primitives in frequency-based QIP, but many challenges remain.…”
We report experimental realization of high-fidelity photonic quantum gates for frequency-encoded qubits and qutrits based on electro-optic modulation and Fourier-transform pulse shaping. Our frequency version of the Hadamard gate offers near-unity fidelity (0.99998 ± 0.00003), requires only a single microwave drive tone for near-ideal performance, functions across the entire C-band (1530-1570 nm), and can operate concurrently on multiple qubits spaced as tightly as four frequency modes apart, with no observable degradation in the fidelity. For qutrits we implement a 3 × 3 extension of the Hadamard gate: the balanced tritter. This tritter-the first ever demonstrated for frequency modes-attains fidelity 0.9989 ± 0.0004. These gates represent important building blocks toward scalable, high-fidelity quantum information processing based on frequency encoding.Introduction.-The coherent translation of quantum states from one frequency to another via optical nonlinearites has been the focus of considerable research since the early 1990s [1]; yet only fairly recently have such processes been explored in the more elaborate context of time-frequency quantum information processing (QIP), where optical frequency is not just the carrier of quantum information but the information itself. Important examples include the quantum pulse gate [2,3], which uses nonlinear mixing with shaped classical pulses for selective conversion of the time-frequency modes of single photons [4][5][6], and demonstrations of frequency beamsplitters based on both χ (2) [7,8] and χ (3) [9][10][11] nonlinearities, which interfere two wavelength modes analogously to a spatial beamsplitter. These seminal experiments have shown key primitives in frequency-based QIP, but many challenges remain. 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. In this Letter, we apply this paradigm to experimentally demonstrate the first electro-optic-based frequency beamsplitter. Our frequency beamsplitter attains high fidelity, operates in * lougovskip@ornl.gov parallel on multiple two-mode subsets across the entire optical C-band, and retains excellent performance at the single-photon level. Moreover, by incorporating an additional harmonic in the microwave drive signal, we also realize a balanced frequency tritter, the threemode extension of the beamsplitter. This is the first frequency tritter demonstrated on any platform, and establishes our electro...
“…Important examples include the quantum pulse gate [2,3], which uses nonlinear mixing with shaped classical pulses for selective conversion of the time-frequency modes of single photons [4][5][6], and demonstrations of frequency beamsplitters based on both χ (2) [7,8] and χ (3) [9][10][11] nonlinearities, which interfere two wavelength modes analogously to a spatial beamsplitter. These seminal experiments have shown key primitives in frequency-based QIP, but many challenges remain.…”
We report experimental realization of high-fidelity photonic quantum gates for frequency-encoded qubits and qutrits based on electro-optic modulation and Fourier-transform pulse shaping. Our frequency version of the Hadamard gate offers near-unity fidelity (0.99998 ± 0.00003), requires only a single microwave drive tone for near-ideal performance, functions across the entire C-band (1530-1570 nm), and can operate concurrently on multiple qubits spaced as tightly as four frequency modes apart, with no observable degradation in the fidelity. For qutrits we implement a 3 × 3 extension of the Hadamard gate: the balanced tritter. This tritter-the first ever demonstrated for frequency modes-attains fidelity 0.9989 ± 0.0004. These gates represent important building blocks toward scalable, high-fidelity quantum information processing based on frequency encoding.Introduction.-The coherent translation of quantum states from one frequency to another via optical nonlinearites has been the focus of considerable research since the early 1990s [1]; yet only fairly recently have such processes been explored in the more elaborate context of time-frequency quantum information processing (QIP), where optical frequency is not just the carrier of quantum information but the information itself. Important examples include the quantum pulse gate [2,3], which uses nonlinear mixing with shaped classical pulses for selective conversion of the time-frequency modes of single photons [4][5][6], and demonstrations of frequency beamsplitters based on both χ (2) [7,8] and χ (3) [9][10][11] nonlinearities, which interfere two wavelength modes analogously to a spatial beamsplitter. These seminal experiments have shown key primitives in frequency-based QIP, but many challenges remain. 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. In this Letter, we apply this paradigm to experimentally demonstrate the first electro-optic-based frequency beamsplitter. Our frequency beamsplitter attains high fidelity, operates in * lougovskip@ornl.gov parallel on multiple two-mode subsets across the entire optical C-band, and retains excellent performance at the single-photon level. Moreover, by incorporating an additional harmonic in the microwave drive signal, we also realize a balanced frequency tritter, the threemode extension of the beamsplitter. This is the first frequency tritter demonstrated on any platform, and establishes our electro...
“…Time-frequency mode selection.-The key experimental requirement to enable this advantage is mode-selective projective measurement in the time-frequency domain. We implement such measurements using a technique known as the quantum pulse gate [36][37][38][39][40], a sum-frequency process where a weak input signal is mixed with a spectrally shaped pump pulse to create an upconverted signal in a long nonlinear waveguide. To implement a quantum pulse gate, the input signal and pump pulses must have matched group velocities and the walkoff between the input and upconverted signals must be longer than the length of the input pulses.…”
By projecting onto complex optical mode profiles, it is possible to estimate arbitrarily small separations between objects with quantum-limited precision, free of uncertainty arising from overlapping intensity profiles. Here we extend these techniques to the time-frequency domain using mode-selective sum-frequency generation with shaped ultrafast pulses. We experimentally resolve temporal and spectral separations between incoherent mixtures of single-photon level signals ten times smaller than their optical bandwidths with a tenfold improvement in precision over the intensity-only Cramér-Rao bound.
“…This selectivity is on par with the value (~9 dB) reported in ref. 14 for a much longer PPLN waveguide (~6 cm) while it shows >40% improvement compared with those in refs 17, 31 at almost the same level of conversion efficiency.Figure 9Selective conversion versus signal-pump delay. Measured and simulated SF power for the second example described in Section 2.3, where the signals correspond to the first two modes of a Gaussian TF filter, and the pump is optimized to selectively convert Signal 1 with a 2-ps pulse width.
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Selective detection of signal over noise is essential to measurement and signal processing. Time-frequency filtering has been the standard approach for the optimal detection of non-stationary signals. However, there is a fundamental tradeoff between the signal detection efficiency and the amount of undesirable noise detected simultaneously, which restricts its uses under weak signal yet strong noise conditions. Here, we demonstrate quantum parametric mode sorting based on nonlinear optics at the edge of phase matching to improve the tradeoff. By tailoring the nonlinear process in a commercial lithium-niobate waveguide through optical arbitrary waveform generation, we demonstrate highly selective detection of picosecond signals overlapping temporally and spectrally but in orthogonal time-frequency modes as well as against broadband noise, with performance well exceeding the theoretical limit of the optimized time-frequency filtering. We also verify that our device does not introduce any significant quantum noise to the detected signal and demonstrate faithful detection of pico-second single photons. Together, these results point to unexplored opportunities in measurement and signal processing under challenging conditions, such as photon-starving quantum applications.
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