Design of Wavelength-Division-Multiplexed Quantum Linear Optical Circuit

Jonathan C. F. Matthews, Alberto Politi, André Stefanov +14 more

Shufeng Li, Xiaosong Yu, Yongli Zhao +3 more

We propose a routing and wavelength allocation method in spatial division multiplexing (SDM) based on quantum key distribution (QKD) optical networks. Especially, for the routing and wavelength allocation of quantum services, we design an auxilia/y matrix-based core allocation and a routing method based on inter-core crosstalk (IC-XT) evaluation. For classic services in SDM optical networks, we design a resource allocation method. Through the proposed hybrid resource allocation strategy, the IC-XT of quantum services can be reducedt Moreover, the amount of available secret keys stored by the node has also increased in SDM optical networks.

Sima Bahrani, Mohsen Razavi, Jawad A. Salehi

We propose orthogonal frequency-division multiplexing (OFDM), as a spectrally efficient multiplexing technique, for quantum key distribution at the core of trusted-node quantum networks. Two main schemes are proposed and analyzed in detail, considering system imperfections, specifically, time misalignment issues. It turns out that while multiple service providers can share the network infrastructure using the proposed multiplexing techniques, no gain in the total secret key generation rate is obtained if one uses conventional passive all-optical OFDM decoders. To achieve a linear increase in the key rate with the number of channels, an alternative active setup for OFDM decoding is proposed, which employs an optical switch in addition to conventional passive circuits. We show that by using our proposed decoder, the bandwidth utilization is considerably improved as compared to conventional wavelength-division multiplexing techniques.

Jonathan C. F. Matthews, Alberto Politi, Anthony Laing +12 more

Ali W. Elshaari, Wolfram H. P. Pernice, Kartik A. Srinivasan +2 more

Aruto Hosaka, Tsubasa Otsuka, Masaya Tomita +1 more

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)).