We propose a large-scale quantum simulator by multiplexing optical quantum modes in the frequency domain and arbitrarily mixing them as a boson sampling optical circuit to obtain Franc Condon Factor of large molecules. By shaping 785-nm femtosecond pump laser pulses, we generate multimode squeezed states via spontaneous parametric down conversion with a type-II PPKTP. Sum frequency mixing using a type-II PPLN between the multimode squeezed states and gate pulses that are shaped to the arbitrary superposition of the multi-spectral mode functions acts as programmable quantum gating. We complete the quantum simulation by time-dependent photon number detection at the sum-frequency wavelength at 517 nm. We describe the advantage of quantum mode manipulation in the frequency domain and place a special emphasis on group velocity dispersion engineering required to achieve them.
We propose a large-scale quantum simulator by multiplexing optical quantum modes in the frequency domain and arbitrarily mixing them as a boson sampling optical circuit to obtain Franc Condon Factor of large molecules. By shaping 785-nm femtosecond pump laser pulses, we generate multimode squeezed states via spontaneous parametric down conversion with a type-II PPKTP. Sum frequency mixing using a type-II PPLN between the multimode squeezed states and gate pulses that are shaped to the arbitrary superposition of the multi-spectral mode functions acts as programmable quantum gating. We complete the quantum simulation by time-dependent photon number detection at the sum-frequency wavelength at 517 nm. We describe the advantage of quantum mode manipulation in the frequency domain and place a special emphasis on group velocity dispersion engineering required to achieve them.
Summary form only given. Optical linear circuit is one of the most important parts for optical quantum computing. The optical circuit, which consists of mode mixers and phase shifters, has been used in various quantum protocols: cluster state generation, Boson sampling, and quantum random walk. To realize a large-scale linear circuit, waveguide-based quantum circuits have experimentally been demonstrated by some groups [1, 2]. However, such a waveguide-based circuit cannot overcome issues of flexibility and loss.On the other hand, recently, a quantum pulse gate (QPG), which enables mode extraction from multimode quantum fields in the frequency domain, has been proposed and experimentally demonstrated [3]. For utilizing the frequency resource of photon field, parallel generations of single photons or multimode squeezed states in the frequency domain, namely time-frequency Schmidt modes, have been demonstrated. In such a wavelengthdivision-multiplexed quantum circuit, this mode extraction corresponds to one row of a linear unitary rotation of the Schmidt modes. It is achieved by sum frequency generation between a spectrally-shaped classical pulse and a quantum weak pulse. The arbitrary mode extraction can be designed by the pulse shaping with a high efficiency. In this report, we propose a multistage QPG which is a simple, flexible and highly efficient quantum linear optical circuit. We devised a novel multipass 4-f system to map the frequency multimode quantum states into the spatiotemporal domain with a single nonlinear crystal (Fig. 1(a)). Furthermore, we show its application to a quantum simulator for calculating molecular vibronic absorption spectra [4] (Fig. 1(b)).
Continuous variable encoding of quantum information requires the deterministic generation of highly correlated quantum states of light in the form of quantum networks, which, in turn, necessitates the controlled generation of a large number of squeezed modes. In this paper, we present an experimental source of multimode squeezed states of light at telecommunication wavelengths. Generation at such wavelengths is especially important as it can enable quantum information processing, communication, and sensing beyond the laboratory scale. We use a single-pass spontaneous parametric down-conversion process in a nonlinear waveguide pumped with the second harmonic of a femtosecond laser. Our measurements reveal significant squeezing in more than 21 frequency modes, with a maximum squeezing value exceeding 2.5 dB. We demonstrate multiparty entanglement by measuring the state's covariance matrix. Finally, we show the source reconfigurability by preparing few-node cluster states and measure their nullifier squeezing level. These results pave the way for a scalable implementation of continuous variable quantum information protocols at telecommunication wavelengths, particularly for multiparty, entanglement-based quantum communications. Moreover, the source is compatible with additional pulse-by-pulse multiplexing, which can be utilized to construct the necessary three-dimensional entangled structures for quantum computing protocols. Published by the American Physical Society 2024
Full control over the spatiotemporal structure of quantum states of light is an important goal in quantum optics, to generate, for instance, single-mode quantum pulses or to encode information on multiple modes, enhancing channel capacities. Quantum light pulses feature an inherent, rich spectral broadband-mode structure. In recent years, exploring the use of integrated optics as well as source engineering has led to a deep understanding of the pulse-mode structure of guided quantum states of light. In addition, several groups have started to investigate the manipulation of quantum states by means of single-photon frequency conversion. In this paper, we explore new routes towards complete control of the inherent pulse-modes of ultrafast pulsed quantum states by employing specifically designed nonlinear waveguides with adapted dispersion properties. Starting from our recently proposed quantum pulse gate (QPG), we further generalize the concept of spatiospectral engineering for arbitrary χ (2) -based quantum processes. We analyse the sum-frequency generation-based QPG and introduce the difference-frequency generation-based quantum pulse shaper (QPS). Together, these versatile and robust integrated optical devices allow for arbitrary manipulations of the pulse-mode structure of ultrafast pulsed quantum states. The QPG can be utilized to select an arbitrary pulse mode from a multimode input state, whereas the QPS enables the generation of specific pulse modes from an input wavepacket with a Gaussian-shaped spectrum.
We introduce the concept of a quantum pulse gate (QPG), a method for accessing the intrinsic broadband spectral mode structure of ultrafast quantum states of light. This mode structure can now be harnessed for applications in quantum information processing. We propose an implementation in a PPLN waveguide, based on spectrally engineered sum frequency generation (SFG). It allows us to pick well-defined spectral broadband modes from an ultrafast multi-mode state for interconversion to a broadband mode at another frequency. By pulse-shaping the bright SFG pump beam, different orthogonal broadband modes can be addressed individually and extracted with high fidelity. (C) 2011 Optical Society of America
In this paper, we propose a novel method for interfering frequency-multiplexed photonic quantum states without the use of optical nonlinear effects, and experimentally demonstrate this technique via frequency-domain Hong-Ou-Mandel (HOM) interference. By cascading the generation of quantum states onto arbitrary orthogonal modes, we can induce interference across any desired frequency mode. Following the generation of quantum states onto the frequency modes, performing measurements in independent frequency bands enables the realisation of a frequency-domain linear optical circuit analogous to linear interference in the spatial domain. We successfully demonstrated programmable quantum interference by controlling the spectral mode functions and measurement bases. Our method offers a new approach to harness the full potential of light's temporal-frequency degrees of freedom, providing a path towards scalable and programmable photonic quantum computing architectures without the need for optical nonlinearities or spatial-mode beam splitters.