We show that waveguides with a dielectric core and a lossy metamaterial cladding (metamaterial-dielectric guides) can support hybrid ordinary-surface modes previously only known for metal-dielectric waveguides. These hybrid modes are potentially useful for frequency filtering applications as sharp changes in field attenuation occur at tailorable frequencies. Our results also show that the surface modes of a metamaterial-dielectric waveguide with comparable electric and magnetic losses can be less lossy than the surface modes of an analogous metal-dielectric waveguide with electric losses alone. Through a characterization of both slab and cylindrical metamaterial-dielectric guides, we find that the surface modes of the cylindrical guides show promise as candidates for all-optical control of low-intensity pulses.Comment: 15 pages, 11 figures. Accepted by Photonics and Nanostructures - Fundamentals and Applications. This version: Title is extended. Section 3 (Modes) and 4 (Characterization) are revised. The abstract, discussion and summary are also revised accordingl
Coherent pulse control for quantum memory is viable in the optical domain but nascent in microwave quantum circuits. We show how to realize coherent storage and on-demand pulse retrieval entirely within a superconducting circuit by exploiting and extending existing electromagnetically induced transparency technology in superconducting quantum circuits. Our scheme employs a linear array of superconducting artificial atoms coupled to a microwave transmission line.
Metamaterial is promising for enhancing the capability of plasmonic devices. We consider a cylindrical waveguide with three-level \Lambda\ atoms embedded in the dielectric core. By comparing metal cladding vs metamaterial cladding of a waveguide with \Lambda\ atoms in the core, we show that, for a fixed amount of slowing of light due to electromagnetically induced transparency, the metamaterial cladding outperforms in terms of the inherent loss.Comment: 8 Pages, 6 figure
An optical quantum memory scheme using two narrow-linewidth cavities and some optical fibers is proposed. The cavities are connected via an optical fiber, and the gap of each cavity can be adjusted to allow photons with a certain bandwidth to transmit through or reflect back. Hence, each cavity acts as a shutter and the photons can be stored in the optical fiber between the cavities at will. We investigate the feasibility of using this device in storing a single photon. We estimate that with current technology storage of a photon qubit for up to 50 clock cycles ͑round trips͒ could be achieved with a probability of success of 85%. We discuss how this figure could be improved.
In principle the Zeno effect controlled-sign gate of Franson et al's (PRA 70, 062302, 2004) is a deterministic two-qubit optical gate. However, when realistic values of photon loss are considered its fidelity is significantly reduced. Here we consider the use of measurement based quantum processing techniques to enhance the operation of the Zeno gate. With the help of quantum teleportation, we show that it is possible to achieve a Zeno CNOT gate (GC-Zeno gate) that gives (near) unit fidelity and moderate probability of success of 0.76 with a one-photon to two-photon transmission ratio κ = 10 4 . We include some mode-mismatch effects and estimate the bounds on the mode overlap and κ for which fault tolerant operation would be possible.
Optical͑2͒ nonlinearity can be used for parametric amplification and producing down-converted entangled photon pairs that have broad applications. It is known that weak nonlinear media exhibit dispersion and produce a frequency response. It is therefore of interest to know how spectral effects of a strong ͑2͒ crystal affect the performance. Here we model the spectral effects of the dispersion of a strong ͑2͒ crystal and illustrate how this affects its ability to perform Bell measurements and influence the performance of a quantum gates that employ such a Bell measurement. We show that a Dyson series expansion of the unitary operator is necessary in general, leading to unwanted spectral entanglement. We identify a limiting situation employing periodic poling, in which a Taylor series expansion is a good approximation and this entanglement can be removed.
We have modeled the Zeno effect controlled-sign gate of Franson et al. ͓Phys. Rev. A 70, 062302 ͑2004͔͒ and shown that high two-photon to one-photon absorption ratios, , are needed for high fidelity free-standing operation. Hence we instead employ this gate for cluster state fusion, where the requirement for is less restrictive. With the help of partially offline one-photon and two-photon distillations, we can achieve a fusion gate with unity fidelity but nonunit probability of success. We conclude that for Ͼ 2200, the Zeno fusion gate will out perform the equivalent linear optics gate.
We have shown that high two-photon to one-photon absorption ratios are needed for a high fidelity free-standing Zeno CZ gate. Nevertheless, using this gate with distillation for cluster fusion can outperform linear optics fusion gate.Despite considerable progress has been made on implementing two qubit gates in optics, the number of photons and gate operations required to implement a near deterministic two qubit gate remains high. A possible solution to this problem is the optical quantum Zeno gate suggested by Franson et al [1,2]. Here we consider a model of the gate that includes the effects of finite two-photon absorption and non-negligible single photon absorption. We obtain the fidelity of the gate and its probability of success in several scenarios and show how the inclusion of optical distilling elements [3] can lead to high fidelity operation under non-ideal conditions for tasks such as cluster state construction [4]. FIG. 1: Construction of our CZ gate. Fig 2. Dual rail implementation of CZ gate Franson et al [1]suggested using a pair of optical fibers weakly evanescently coupled and doped with twophoton absorbing atoms to implement the gate. As the photons in the two fiber modes couple the occurrence of twophoton state components is suppressed by the presence of the two-photon absorbers via the Zeno effect. After a length of fiber corresponding to a complete swap of the two modes a pi phase difference is produced between the |11> term and the others. If the fiber modes are then swapped back by simply crossing them, a CZ gate is achieved. We model this system as a succession of n weak beamsplitters followed by 2-photon absorbers as shown in Fig. 1. As n tends to infinity, the model tends to the continuous coupling limit envisaged for the physical realization. The gate operates on the single-rail encoding [5]. Fig. 2 shows how the single rail CZ can be converted into a dual rail CZ, where polarization photons |H> and |V> are used as logical states zero and one respectively. The input states |HH>, |HV>, |VH>, |VV> corresponds to |00>, |01>, |10>, |11> number states entering the CZ gate.Realistic two-photon absorbers scatter (single) photons and probabilistically absorb two-photons. This causes both single photon and two-photon loss, which lead to some probability amplitude reduction for |01> and |10> states and a relatively larger reduction for |11>. If this imbalance of probability amplitude for the four computational states is significant, the fidelity of this gate would be low. Fig 3. shows that the fidelity of this CZ gate is only close to unity when kappa is large (i.e. little single photon loss). Kappa is the power ratio between the absorber's singlephoton (exp(-lambda/(n*kappa))) and two-photon (exp(-lambda/n)) transmission probabilities. When kappa is large, the Zeno gate works well. (Here, lambda=chi*L, where L is the total length of all absorbers and chi is related to the absorption cross section of the absorbers.) We need a kappa of 10^6 to give fidelity >0.99, and a kappa of 10^8 to give fideli...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.