Multi-Output Nondestructive Controlled Quantum Teleportation Through a Partially Entangled Channel

A new representation of an arbitrary and unknown N-particle state is presented at first. As an application, a scheme for teleporting an arbitrary and unknown N-particle state is proposed when N pairs of two-particle non-maximally entangled states are utilized as quantum channels. After Alice (sender) makes Bell-state measurement on her particles, Bob (recipient) introduces an auxiliary particle and carries out appropriate unitary transformation on his particle and the auxiliary particle depending on classical information from Alice. Then, von Neumann measurement that confirms whether the teleportation succeeds or not is performed by Bob on the auxiliary particle. In order to complete the teleportation, another N-1 times operations need to be performed which are similar to the above ones. It can be successfully realized with a certain probability which is determined by the product of the smaller coefficients of non-maximally entangled pairs. All possible unitary transformations are given in detail.

The purpose of this paper is to explore how to teleport a low-dimensional (two-dimensional) arbitrary unknown two-qubit cat-like state through a high-dimensional entangled state constituting the quantum channel. We first present a scheme employing a maximally entangled three-qutrit state as the channel. Within this scheme, the sender performs a single-qubit projective measurement and a non-symmetric basis measurement on their particles. Based on these measurement outcomes, the receiver applies specific unitary operations to reconstruct the original cat-like state. Subsequently, the maximally entangled channel is replaced with a non-maximally entangled three-qutrit state. For this probabilistic teleportation scheme, the target state is reconstructed by introducing an auxiliary qubit and performing appropriate operations; the corresponding success probability is derived. Analysis indicates that the non-maximally entangled scheme generalizes the previous maximally entangled approach. Furthermore, both schemes are shown to be directly extendable to quantum channels formed by arbitrary high-dimensional entangled states.

We propose a scheme for cloning an arbitrary unknown two-qubit state and its orthogonal complement state with the assistance from the state preparer. Our scheme includes two stages. The first stage requires a quantum teleportation process, in which an arbitrary unknown two-qubit state can be deterministically teleported from the sender to the receiver with χ-type entangled states as the quantum channel. In the second stage, with the assistance of the state preparer, either a perfect copy or an orthogonal complement state of an arbitrary unknown two-qubit state can be obtained with a certain probability.

Generalized quantum state sharing of arbitrary unknown two-qubit state

The capability to generate and manipulate quantum states in high-dimensional Hilbert spaces is a crucial step for the development of quantum technologies, from quantum communication to quantum computation. One-dimensional quantum walk dynamics represents a valid tool in the task of engineering arbitrary quantum states. Here we affirm such potential in a linear-optics platform that realizes discrete-time quantum walks in the orbital angular momentum degree of freedom of photons. Different classes of relevant qudit states in a six-dimensional space are prepared and measured, confirming the feasibility of the protocol. Our results represent a further investigation of quantum walk dynamics in photonics platforms, paving the way for the use of such a quantum state-engineering toolbox for a large range of applications.

Higher dimensional Hilbert space along with ability to control multiple degrees of freedom of photon and entangle them has enabled new quantum protocols for various quantum information processing applications. Here, we propose a scheme to generate and control polarization-path-frequency entanglement using the operative elements required to implement a polarization-controlled quantum walk in the path (position) space and frequency domain. Hyperentangled states manifests in the controlled dynamics using an interferometric setup where half-wave plates, beam-splitters and frequency shifters such as those based on the electro-optic effect are used to manipulate the polarization, path and frequency degrees of freedom respectively. The emphasis is on utilizing the polarization to influence the movement to a specific value in the frequency and position space. Negativity between the subspaces is calculated to demonstrate the controllability of the entanglement between the three degrees of freedom and the effect of noise on the entanglement is modelled using the depolarizing channel. Progress reported with experimental demonstration of realization of quantum walk using quantum states of light makes quantum walks a practical approach to generate hyperentangled states.

High-dimensional Hilbert spaces used for quantum communication channels offer the possibility of large data transmission capabilities. We propose a method of characterizing the channel capacity of an entangled photonic state in high-dimensional position and momentum bases. We use this method to measure the channel capacity of a parametric down-conversion state by measuring in up to 576 dimensions per detector. We achieve a channel capacity over 7 bits/photon in either the position or momentum basis. Furthermore, we provide a correspondingly high-dimensional separability bound that suggests that the channel performance cannot be replicated classically.

A scheme of circular controlled quantum teleportation, which is a novel version of bidirectional controlled quantum teleportation, is proposed using a specific genuine seven-qubit entangled state as quantum channel, and then it is generalized to the scene with a general genuine seven-qubit entangled state as channel. This means that with the control of the supervisor Daniel while Alice teleportates an unknown qubit state to Bob, Bob can also teleportate an unknown qubit state to Charlie and Charlie can also teleportate an unknown qubit state to Alice circularly, simultaneously. Compared with the BCQT schemes proposed before, the intrinsic efficiency of our scheme is optimal.

An N-receiver quantum dense coding scheme, in the case of high-dimensional Hilbert spaces, are investigated in this paper. A sender can send his messages to many receivers simultaneously.

A new scheme for short-distance quantum teleportation of an arbitrary unknown three-dimensional two-qutrit state is proposed, utilizing a three-dimensional Bell-state and a ground-state auxiliary qutrit as quantum channel. In this scheme, both the sender and receiver are required to pre-share an auxiliary qutrit in addition to sharing the three-dimensional Bell state. The sender performs joint measurements on their Bell qutrit and the unknown quantum system after performing quantum gate operations on the auxiliary qutrit, and sends the classical information of the measurement results to the receiver. Based on the measurement results, the receiver converts, with 100% probability, the quantum state of his/her own Bell qutrit and auxiliary qutrit into an exact replica of the unknown quantum state initially altered by the sender. This scheme exhibits advantages such as a short transmission distance, high information capacity, reduced consumption of entanglement resources, and promising applications in quantum teleportation for solid-state devices, such as on-chip implementations.

We present a scheme for quantum state sharing of an arbitrary qudit state by using nonmaximally entangled generalized Greenberger–Horne–Zeilinger (GHZ) states as the quantum channel and generalized Bell-basis states as the joint measurement basis. We show that the probability of successful sharing an unknown qudit state depends on the joint measurements chosen by Alice. We also give an expression for the maximally probability of this scheme.

We investigate the entanglement swapping of the continuous variable states by taking the pair Schrödinger cat states as the input entangled states, in which the two-mode squeezed vacuum and the pair cat states serve as the quantum channel, respectively. The entanglement of the initial states as well as the final states is analyzed by adopting the logarithmic negativity as the measure of entanglement. The quantum teleportation task by exploiting the swapped states as the quantum channel is also considered, where a coherent state serves as the target state and the average fidelity is examined.

Perfect teleportation of arbitrary n-qudit states using different quantum channels

This study introduces the concept of elastic bits in a driven granular metamaterial. These elastic bits function similarly to quantum bits (qubits), but they can maintain more stable superpositions by forming topological braiding structures with robust information stored in their phase. We have recently developed models using classical nonlinear granular metamaterials to simulate quantum-inspired computing. Using a two-coupled granular system, we analyze nonlinear vibrations and eigenstates through molecular dynamics simulations and Fourier analysis to map displacement fields into Hilbert spaces. These models demonstrate states resembling a multipartite two-level quantum system, where each subsystem represents an elastic bit analogous to time-dependent coherent superpositions of elastic bits. The study demonstrates the creation of two and three elastic bits, represented as tensor products of eigenstates in higher-dimensional Hilbert spaces. By manipulating these elastic bits—similar to quantum braiding operations—we can adjust the phase of the wave function. This allows for various types of braiding that enable robust quantum-inspired computations. Notably, “time” serves as the direction of braiding in this setup. [Funding: NSF Grants 2204382 and 2242925.]

Two-photon states entangled in continuous variables such as wavevector or frequency represent a powerful resource for quantum information protocols in higher-dimensional Hilbert spaces. At the same time, there is a problem of addressing separately the corresponding Schmidt modes. We propose a method of engineering two-photon spectral amplitude in such a way that it contains several non-overlapping Schmidt modes, each of which can be filtered losslessly. The method is based on spontaneous parametric down-conversion (SPDC) pumped by radiation with a comb-like spectrum. There are many ways of producing such a spectrum; here we consider the simplest one, namely passing the pump beam through a Fabry-Perot interferometer. For the two-photon spectral amplitude (TPSA) to consist of non-overlapping Schmidt modes, the crystal dispersion dependence, the length of the crystal, the Fabry-Perot free spectral range and its finesse should satisfy certain conditions. We experimentally demonstrate the control of TPSA through these parameters. We also discuss a possibility to realize a similar situation using cavity-based SPDC.