A conditional realization of the single-qubit amplitude damping channel is proposed. Kraus operators are probabilistically realized in dual-rail frequency basis by use of phase modulation and a fiber Bragg grating, resulting in success probabilities >;31.5%.
In a recent paper, have developed a scheme for the stochastic implementation of arbitrary quantum operations on multimode single-photon qudit states by using reconfigurable linear-optic systems. Based on this idea, we explore the use of phase modulation for the realization of qubit channels in the frequency basis. Single-photon states belonging to two different frequency modes differing by the modulator's driving frequency represent the input dual-rail qubit states. The channel is implemented by a phase modulator followed by a fiber Bragg grating, taking advantage of the high degree of reconfigurability and microwave bandwidth shown by electrooptic modulation technology. The channels are realized by a combination of three techniques: 1) suitably designed driving waveforms, which are probabilistically addressed to the modulator; 2) the corresponding addressing probabilities; and 3) the grating transmittance at the values of the frequency basis. The proposed scheme results in nonoptimal success probabilities but is shown to allow for a compact implementation of the conventional qubit random unitary channels and the qubit amplitude-damping channel.
We experimentally demonstrate a single-qubit decohering quantum channel using linear optics. We implement the channel, whose special cases include the familiar amplitude-damping channel and the bit-flip channel, using a single, static optical setup. Following a recent theoretical result (Piani et al 2011 Phys. Rev. A 84 032304), we realize the channel in an optimal way, maximizing the probability of success, i.e. the probability for the photonic qubit to remain in its encoding. Using a two-photon entangled resource, we characterize the channel using ancilla-assisted process tomography and find average process fidelities of 0.98 ± 0.01 and 0.976 ± 0.009 for amplitude-damping and the bit-flip case, respectively.
This thesis deals with the implementation of quantum channels using linear optics. We begin with overviews of some important concepts in both quantum information and quantum optics. First, we discuss the quantum bit and describe the evolution of the states via quantum channels. We then discuss both quantum state and process tomography, methods for how to determine which states and operations we are experimentally implementing in the lab. Second, we discuss topics in quantum optics such the generation of single photons, polarization entanglement, and the construction of an entangling gate. \n \nThe first experiment is the implementation of a quantum damping channel, which intentionally can add a specific type and amount of decohering noise to a photonic qubit. Specifically, we realized a class of quantum channels which contains both the amplitude-damping channel and the bit-flip channel, and did so with a single, static, optical setup. Many quantum channels, and some gates, can only be implemented probabilistically when using linear optics and postselection. Our main result is that the optical setup achieves the optimal success probability for each channel. Using a novel ancilla-assisted tomography, we characterize each case of the channel, and find process fideilities of 0.98pm0.01 for the amplitude-damping channel and 0.976pm0.009 for the bit-flip. \n \nThe second experiment is an implementation of a protocol for quantum computing on encrypted data. The protocol provides the means for a client with very limited quantum power to use a server's quantum computer while maintaining privacy over the data. We perform a quantum process tomography for each gate in a universal set, showing that only when the proper decryption key is used on the output states, which is hidden from the server, then the action of the quantum gate is recovered. Otherwise, the gate acts as the completely depolarizing channel.
We propose and theoretically study a method for the stochastic realization of arbitrary quantum channels on multimode single-photon qudits. In order for our method to be undemanding in its implementation, we restrict our analysis to linear-optical techniques, vacuum ancillary states, and nonadaptive schemes, but we allow for random switching between different optical networks. With our method it is possible to deterministically implement random-unitary channels and to stochastically implement general channels. We provide an expression for the optimal probability of success of our scheme and calculate this quantity for specific examples such as the qubit amplitude-damping channel. The success probability is shown to be related to the entanglement properties of the Choi-Jamio\l{}kowski state isomorphic to the channel.
In this paper, two conclusive multiparty quantum operation sharing (QOS) schemes in amplitude damping channel are proposed to respectively share partially unknown single-qubit unitary operations and single-qutrit unitary operations from the different restricted sets. To reach this target, the detail procedures of using entanglement compensation in amplitude damped channel to share pure entangled quantum states is first proposed. Then, using the pure entangled quantum state shared between the two sender and their two agents as a quantum channel, the dealer’s secret quantum operation, i.e. partially unknown single-qubit unitary operation (or partially unknown single-qutrit unitary operation) can be remotely implemented by the dealer at any one of the locations of all the agents in such way that the unknown quantum state after being acted on by this quantum operation can be probabilistically reconstructed through introducing an auxiliary qubit and performing appropriate local operations provided that two agents collaborate together. Subsequently, the above two schemes are generalized from 2 agents to the scenario of [Formula: see text] ([Formula: see text]) agents. In addition, through our analysis, we have found that in both single-qubit and single-qutrit QOS schemes, the probability of successful recovery of the target state by the receiver after the quantum operation is solely determined by the smaller of the absolute values of the coefficients that characterize the quantum channel. This proves that, under the same amplitude damping strength, the conclusive multiparty single-qutrit QOS has a higher success probability than the single-qubit QOS.