Entangled photon states generation and regeneration using a nonlinear fiber ring resonator

We propose a simple system of the entangled photon states generation and regeneration using a standard diode laser, a Mach Zehnder Interferometer (MZI) and a fiber optic ring resonator (FORR). Light from the diode laser is launched into an MZI and circulated in the FOOR, without any optical pumping components included in the system. The nonlinear light pulses are generated by a Kerr nonlinear effects type, while the resonance peaks are formed by the four-wave mixing of light pulses in the FORR. The entangled photons can be performed by using the polarization control device, and then detected by the avalanche photo-detectors, where the entangled photon visibility is plotted and seen. Similarly, the entangled photon states can be easily formed by using the appropriated coupling ratios into a fiber coupler, then into a ring resonator, i.e. without an MZI. The use of the entangled photons generation based on a fiber optic scheme for quantum teleportation, quantum key distribution via optical wireless link, and the system of the entangled photon states recovery by using a fiber ring resonator incorporating an erbium-doped fiber (EDF) have been investigated and discussed. The feasibility of dense coding using multi-entangled photons generation based on the fiber optic scheme and the effect of the entangled state walk-off along the optical fiber are also discussed, respectively.     

Polarized soliton pulses generation using nonlinear micro ring resonators for multi- and long distance links

We propose a new concept of quantum soliton pulses generation using a soliton pulse in the micro ring resonators. Firstly, the chaotic soliton pulses are generated and circulated within the integrated micro ring resonators. Secondly, the specific second harmonic pulses are selected by using the appropriate ring parameters. The superposition of the second harmonic pulses within the micro ring devices introduces the randomly polarized photons within the micro ring device. The entangled photon visibility of the polarized photon is seen after passing the polarization control devices and projecting on the detectors. The optimum entangled photon visibility is obtained. The advantage of such a system is that the quantum repeater unit can be redundant for long distance quantum communication link, whereas the use of the system for multi-entangled photon sources and links is also available. The system degradation via the entangled photon states timing walk-off is also discussed.     

A simultaneous generation of QKD and QDC via optical memory array for distributed network security

We propose a novel system of a simultaneous generation of continuous variable quantum key distribution (QKD) and quantum dense coding (QDC) via an optical memory array. The optical memory system is formed by using an array waveguide incorporating a nano-ring resonator, whereas the different spatial light modes can be generated and stored within an optical memory unit. The polarized photon is formed and stored within a storing device, i.e. a ring resonator, whereas the different time slot entangled photons can be generated, transmitted and detected by the different subscriber in the distributed networks. By using the optical memory concept, the continuous variable quantum key distribution is provided. Furthermore, the use of quantum dense coding via time division multiplexing paths, i.e. different time slot, is also plausible. The advantage of the proposed system is that the quantum key distribution can provide the network top security with high capacity and safety, which is the large demand of usage in the public networks.     

QKD and QDC via optical-wireless link for quantum mobile telephone network application

We propose a novel system of the simultaneous continuous variable quantum key distribution (QKD) and quantum dense coding (QDC) using a soliton pulse within the nonlinear micro-ring resonator devices. By using the appropriate soliton input power and nonlinear micro-ring parameters, the continuous signals are generated spreading over the spectrum. The polarized photons are formed by using the polarization control unit incorporating into the micro-ring system, which is allowed the different time slot entangled photon pair randomly formed. Results obtained have shown that the application of such a system for the simultaneous continuous variable quantum cryptography and dense coding within a single system is plausible, which is can be implemented within the mobile telephone hand set and networks.     

Second-harmonic generation via micro ring resonators for optimum entangled photon visibility

An analysis of a new technique for quantum key distribution (QKD) using the entangled photon within a micro ring resonator is presented. The Kerr nonlinear type of light in the micro ring resonator induces the nonlinear behavior known as chaos within the device, where the superposition of the chaotic signals via a four-wave mixing type introduces the clear second-harmonic pulses. The generation of clear second-harmonic pulses is achieved by controlling the appropriate ring parameters. When the polarization control devices are applied into the system, the optimal entangle photon visibility is obtained. The condition for long-distance link is discussed, where the optimal entangled photon visibility in term of Bell's states is described.     

Quantum key distribution using the localized soliton pulses via a wavelength router in the optical network

We propose a new system of a continuous variable quantum key distribution via a wavelength router in the optical networks. A large bandwidth signal is generated by a soliton pulse propagating within the micro ring resonator, which is allowed to form the continuous wavelength with large tunable channel capacity. There are two forms of localized soliton pulses proposed. Firstly, the required information is transmitted via the localized temporal soliton pulse. Secondly, the continuous variable quantum key distribution is formed by using the localized spatial soliton pulse via a quantum router and networks, which is formed by using and optical add/drop multiplexer incorporating in the network. The localized soliton pulses are available for add/drop signals to/from the optical network, where the high security and capacity information can be performed.     

Quantum bits generation using correlated photons: Fidelity and error corrections

We propose a new system of quantum bits generation using a soliton pulse within a micro ring resonator. A quantum gate can be formed using a polarization control unit incorporating into the system. The random signal and idler pairs can be formed within the photon correlation bandwidth, which can be generated and randomly formed the packet quantum bits, i.e. quantum packet codes. Each random code (logic) can be performed by combining the signal and idler of each entangled photon pair via the quantum gate. Results obtained have shown that the packet of quantum logic bits can be generated using the entangled photon pairs generated by the proposed system. The quantum bits transmission fidelity and error corrections are also described.     

Continuous variable quantum key distribution via a simultaneous optical-wireless up-down-link system

We propose a remarkably simple system of a continuous variable quantum key distribution using chaotic signals generated by a soliton pulse within a nonlinear micro-ring resonator system. By using the appropriate soliton input power and micro-ring parameters, continuous signals are generated spreading over the spectrum. Polarized photons are formed incorporating the polarization control unit into the micro-ring system, which allows different time slot entangled photons to be randomly formed. Two different frequency bands for up-down-link converters can be selected (filtered) and performed, which is available for the simultaneous up-down-link application in the telephone networks. Results obtained have shown that the application of such a system for continuous variable quantum cryptography via optical-wireless up-down-link converters within a single system is plausible.     

Error corrections of quantum key distribution of the quantum codes via optical wireless link

Quantum key generated by using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator is proposed. The generated quantum key is distributed via an optical wireless link system, which is available for the free space link. The random quantum bits can be formed and used as the secret codes in quantum communication system. By adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing quantum parity checking, the high fidelity to the noiseless quantum in free space is achieved by the technique known as the quantum error correction.     

A novel multi-optical/quantum memory and encoding system using multi-photon generation

We propose a novel system of an optical/quantum memory generation, which can be used for multi-optical/quantum memory applications. The large bandwidth of a single pulse is generated using a soliton pulse in a Kerr-type nonlinear medium, i.e. a nonlinear waveguide. The generation of the localized temporal and spatial soliton pulses within the nano-waveguide is achieved. The free spectrum range enhancement of the generated multi-soliton signals can be formed and achieved using the nano-waveguide incorporating the Mach Zhender Interferometer (MZI). The different light path of the soliton pulses is introduced by the delayed lines of the interferometer. This improves the wavelength free spectrum range, where the different entangled photon pairs can also obtained. Furthermore, the generated photons can be filtered and stored within a system, where the storage of single or multi-photons using the proposed system can be achieved, which in turn can be used for multi-optical/quantum memory applications.     

Quantum key distribution via fiber optic, fidelity and error corrections

We propose an interesting scheme on photon states generation using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator without any optical pumping parts including in the system, which is available for long-distance link. In principle, the state of a quantum bit, it is known, unknown, or entangled to other systems. The desired quantum states are generated and transmitted in the link via a fiber optic. The transmission quality in terms of quantum fidelity is analyzed, where a high fidelity to the noiseless quantum channel is achieved by adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing the quantum parity checking method. The error correction is also analyzed. For simplicity, feature and robustness against path-length mismatches among the nodes make our scheme suitable for multi-user quantum communication networks.     

Entangled photon states recovery and cloning via the micro ring resonators and an add/drop multiplexer

We propose a new system of the entangled photon generation and recovery using a Gaussian pulse traveling within the nonlinear micro ring resonators, whereas the cloning feasibility of the entangled photon states via an add/drop multiplexer is also proposed. Firstly, the optimum entangled photon visibility is generated by using the Gaussian pulse in the ring resonators, where the second harmonic pulses are generated by filtering the chaotic signals. Secondly, the small amount of the transmission power is coupled by the add/drop device, whereas the entangled photon states, i.e. cloning states, are regenerated by using the polarization control unit. Results obtained have shown that the recovery entangled photon states can be made and confirmed with the initial states, which means that the cloning of entangled photon states of the initial states is plausible. The amplified entangled photon for state recovery is also discussed.     

Quantum packet switching generation using correlated photons in a microring resonator system

We propose a new system of a packet of quantum bits generation using a soliton pulse within a microring resonator. A quantum gate can be formed by using a polarization control unit incorporating into the system. The random signal and idler pairs can be formed within the photon correlation bandwidth, which can be generated, and randomly form the packet quantum bits, i.e. quantum packet switching. Each random code (logic) can be performed by combining the signal and idler of each entangled photon pair via the quantum gate. Results obtained have shown that the packet of quantum logic bits can be generated using the entangled photon pairs generated by the proposed system.     

基于纠缠度计算的量子移动信令相邻小区越区切换策略及仿真

信令是任何通信系统必不可少的重要组成部分,量子移动通信也不例外.然而,关于量子移动通信信令在相邻小区越区切换过程中的切换策略问题的研究迄今尚未展开.随着移动用户位置的改变,用户与基站间的纠缠度不断变化.本文提出了基于纠缠度计算的量子信令在相邻小区的越区切换策略.首先定义了信令纠缠度与距离的关系,然后研究了用户位置改变所导致用户与基站之间信令纠缠度的变化情况,提出了基于纠缠度阈值计算的切换算法.仿真结果表明,本文所提出的信令切换策略可靠性高,能够在各基站之间实现平稳切换.因此,本研究对于构造量子移动通信网络的信令系统及其标准的制定具有极为重要的技术支撑作用.     

Quantum state transfer between light and matter via teleportation

Quantum teleportation is an interesting feature of quantum mechanics. Entanglement is used as a link between two remote locations to transfer a quantum state without physically sending it – a process that cannot be realized utilizing merely classical tools. Furthermore it has become evident that teleportation is also an important element of future quantum networks and it can be an ingredient for quantum computation. This article reports for the first time the teleportation from light to atoms. In the experiment discussed, the quantum state of a light beam is transferred to an atomic ensemble. The key element of light‐atom entanglement created via a dispersive interaction lays the foundation for the protocol.     

Universality of black hole quantum computing

By analyzing the key properties of black holes from the point of view of quantum information, we derive a model‐independent picture of black hole quantum computing. It has been noticed that this picture exhibits striking similarities with quantum critical condensates, allowing the use of a common language to describe quantum computing in both systems. We analyze such quantum computing by allowing coupling to external modes, under the condition that the external influence must be soft‐enough in order not to offset the basic properties of the system. We derive model‐independent bounds on some crucial time‐scales, such as the times of gate operation, decoherence, maximal entanglement and total scrambling. We show that for black hole type quantum computers all these time‐scales are of the order of the black hole half‐life time. Furthermore, we construct explicitly a set of Hamiltonians that generates a universal set of quantum gates for the black hole type computer. We find that the gates work at maximal energy efficiency. Furthermore, we establish a fundamental bound on the complexity of quantum circuits encoded on these systems, and characterize the unitary operations that are implementable. It becomes apparent that the computational power is very limited due to the fact that the black hole life‐time is of the same order of the gate operation time. As a consequence, it is impossible to retrieve its information, within the life‐time of a black hole, by externally coupling to the black hole qubits. However, we show that, in principle, coupling to some of the internal degrees of freedom allows acquiring knowledge about the micro‐state. Still, due to the trivial complexity of operations that can be performed, there is no time advantage over the collection of Hawking radiation and subsequent decoding.     

基于纠缠度计算的量子移动信令相邻小区越区切换策略及仿真

信令是任何通信系统必不可少的重要组成部分,量子移动通信也不例外.然而,关于量子移动通信信令在相邻小区越区切换过程中的切换策略问题的研究迄今尚未展开.随着移动用户位置的改变,用户与基站间的纠缠度不断变化.本文提出了基于纠缠度计算的量子信令在相邻小区的越区切换策略.首先定义了信令纠缠度与距离的关系,然后研究了用户位置改变所导致用户与基站之间信令纠缠度的变化情况,提出了基于纠缠度阈值计算的切换算法.仿真结果表明,本文所提出的信令切换策略可靠性高,能够在各基站之间实现平稳切换.因此,本研究对于构造量子移动通信网络的信令系统及其标准的制定具有极为重要的技术支撑作用.     

Cascading attack on trusted-relay quantum key distribution networks

Trusted relays are the main state-of-the-art way to realize quantum key distribution networks.However, it is hard to require that all nodes in the network are fully trusted. In a multipath keytransmission mechanism, the nodes can be weakly trusted because the secret key can be split into many parts and each part is transmitted to the receiver through a different path. However, if the capacity of a node's quantum key pool is poorly designed, an attacker, Eve may eavesdrop on the communicating parties' secret message by initiating a redirection attack. In this paper, we show that Eve can trigger a cascading collapse effect by collapsing one of the edges in the network and forcing the communication parties to transmit the message through the nodes controlled by Eve. The influence of the traffic transfer ratio and the control parameters of the edge load on the breakdown probability of the edge are analyzed using a simulation. In order to effectively defend against the cascading attack, it is important for the designer to handle the relationship between the traffic and the capacity of the quantum key pool of each node in the network.     

Quantum computers and quantum coherence

If the states of spins in solids can be created, manipulated, and measured at the single-quantum level, an entirely new form of information processing, quantum computing, will be possible. We first give an overview of quantum information processing, showing that the famous Shor speedup of integer factoring is just one of a host of important applications for qubits, including cryptography, counterfeit protection, channel capacity enhancement, distributed computing, and others. We review our proposed spin-quantum dot architecture for a quantum computer, and we indicate a variety of first generation materials, optical, and electrical measurements which should be considered. We analyze the efficiency of a two-dot device as a transmitter of quantum information via the propagation of qubit carriers (i.e. electrons) in a Fermi sea.     

Expandable quantum key distribution networks based on secret bits comparison

A scheme of quantum network based on multiuser differential phase shift quantum key distribution system (DPS-QKD) is proposed. In this quantum network, arbitrary two users can achieve secret bits sharing by point-to-multipoint quantum key distribution and secret bits comparison. A protocol of secret bits sharing between arbitrary two users is presented. This network can implement secret bits distribution over 200 km with higher key generation rate by today's technologies. In theory, the capacity of user numbers in this network is unlimited. Hence, our proposed quantum network can serve for a metropolitan QKD network. A wide area QKD network can be constructed with this metropolitan QKD network.