- 标题
- 摘要
- 关键词
- 实验方案
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Quantum Dialogue Based on Entanglement Swapping and Hadamard Operation via Cavity QED
摘要： A quantum dialogue scheme based on entanglement swapping and Hadamard operation via cavity QED is proposed, which effectively uses the evolution law of atom in cavity QED. The proposed scheme uses Bell states and GHZ states as quantum resource and only needs single-atom measurements. The proposed scheme is secure against active attacks from an eavesdropper and can transmit 4 secret bits per round communication.
关键词： Entanglement swapping,Hadamard operation,Quantum dialogue,Cavity QED
更新于2025-09-23 15:23:52
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Entanglement generation between distant parties via disordered spin chains
摘要： We study the emergence of bipartite entanglement between a pair of spins weakly connected to the ends of a linear disordered X Y spin-1/2 channel. We analyze how their concurrence responds to structural and on-site fluctuations embodied by long-range spatially-correlated sequences. We show that the end-to-end entanglement is very robust against disorder and asymmetries in the channel provided that the degree of correlations are strong enough and both entangling parties are tuned accordingly. Our results offer further alternatives in the design of stable quantum communication protocols via imperfect spin channels.
关键词： Quantum entanglement,Quantum state transfer,Anderson localization
更新于2025-09-23 15:23:52
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Entanglement measures of a new type pseudo-pure state in accelerated frames
摘要： In this work we analyze the characteristics of quantum entanglement of the Dirac field in noninertial reference frames in the context of a new type pseudo-pure state, which is composed of the Bell states. This will help us to understand the relationship between the relativity and quantum information theory. Some states will be changed from entangled states into separable ones around the critical value F = 1/4, but there is no such a critical value for the variable y related to acceleration a. We find that the negativity NABI ((cid:26)TA ABI ) increases with F but decreases with the variable y, while the variation of the negativity NBI BII ((cid:26)TBI BI BII ) is opposite to that of the negativity NABI ((cid:26)TA ABI ). We also study the von Neumann entropies S((cid:26)ABI ) and S((cid:26)BI BII ). We find that the S((cid:26)ABI ) increases with variable y but S((cid:26)BI BII ) is independent of it. However, both S((cid:26)ABI ) and S((cid:26)BI BII ) first decreases with F and then increases with it. The concurrences C((cid:26)ABI ) and C((cid:26)BI BII ) are also discussed. We find that the former decreases with y while the latter increases with y but both of them first increase with F and then decrease with it.
关键词： pseudo-pure state,concurrence,negativity,noninertial frame,entanglement,von Neumann entropy
更新于2025-09-23 15:23:52
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Time evolution of entanglement and trace distance in an atom-cavity system described with random walk and non-random walk states
摘要： An atom-cavity system consists of an atom or group of atoms inside a cavity. When an atom in cavity is stimulated by a laser pump, it is affected by the atom-field interaction shows the qusi- random walk behavior. This can change the entanglement and trace distance of system. In this work, the change entanglement and trace distance of system in two different cases -namely- the random walk and non-random walk is considered. The descriptive system is a two -level atom in the electrodynamics cavity based on the Jayne’s-Cummings model, which is stimulated by two longitudinal and transverse laser pumps. The results show that the consideration of the random walk case for the atom changes in the amount of entanglement can be seen as the phenomenon of sudden death and birth of entanglement. It results in its rate of changes to be increased. In contrast to the non-random walk case, this rate is increased and decreased more quickly compared to the random walk case. The maximum amount of entanglement in each case is the same, but the minimum in random walk case is less than that of non-random walk case.
关键词： entanglement,random walk,trace distance,Cavity,laser pump
更新于2025-09-23 15:23:52
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Multiparty Quantum Key Agreement Based on Three-Photon Entanglement with Unidirectional Qubit Transmission
摘要： A multiparty quantum key agreement protocol based on three-photon entangled states is proposed. In this scheme, the quantum channel between all parties is that of a closed loop, in which the qubit transmission is one-way. Each party can obtain the sum of the other parties’ secret key values through the coding rules instead of extracting their private keys. The shared secret key cannot be determined by any subset of all the participants except the universal set and each party makes an equal contribution to the final key. Moreover, the security analysis shows our protocol can resist both outside attacks and inside attacks.
关键词： Quantum cryptography,Three-photon entanglement,One-way qubit transmission,Quantum key agreement
更新于2025-09-23 15:23:52
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Nonclassical properties of two-mode squeezing-enhanced vacuum state
摘要： We present a new kind of two-mode squeezed vacuum state with two squeezing parameters. Different from the normal univariate two-mode squeezed vacuum state, this new state shows stronger squeezing effect, anti-bunching and entanglement. It is shown that the new squeezing parameter plays an important role in this state.
关键词： fidelity,entanglement,cross-correlation function,squeezing,antibunching effect
更新于2025-09-23 15:23:52
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Entanglement Generation in Superconducting Qubits Using Holonomic Operations
摘要： We investigate a nonadiabatic holonomic operation that enables us to entangle two fixed-frequency superconducting transmon qubits attached to a common bus resonator. Two coherent microwave tones are applied simultaneously to the two qubits and drive transitions between the first excited resonator state and the second excited state of each qubit. The cyclic evolution within this effective three-level Λ-type system gives rise to a holonomic operation entangling the two qubits. Two-qubit states with 95% fidelity, limited mainly by charge noise of the current device, are created within 213 ns. This scheme is a step toward implementation of a SWAP-type gate directly in an all-microwave controlled hardware platform. By extending the available set of two-qubit operations in the fixed-frequency qubit architecture, the proposed scheme may find applications in near-term quantum applications using variational algorithms to efficiently create problem-specific trial states. We illustrate this point by computing the ground state of molecular hydrogen using the holonomic operation.
关键词： holonomic operations,microwave control,entanglement,quantum computing,superconducting qubits
更新于2025-09-23 15:23:52
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Unconventional Rydberg pumping and applications in quantum information processing
摘要： We propose a mechanism of unconventional Rydberg pumping (URP) via simultaneously driving each Rydberg atom by two classical fields with different strengths of Rabi frequencies. This mechanism differs from the general Rydberg blockade or Rydberg antiblockade since it is closely related to the ground states of atoms, i.e., two atoms in the same ground state are stable while two atoms in different ground states are resonantly excited. Furthermore, we find the URP can be employed to simplify some special quantum information processing tasks, such as implementation of a three-qubit controlled-PHASE gate with only a single Rabi oscillation, preparation of two- and three-dimensional steady-state entanglement with two identical atoms, and realization of the autonomous quantum error correction in a Rydberg-atom-cavity system. The feasibility of the above applications is discussed explicitly by the state-of-the-art technology.
关键词： quantum error correction,Rydberg blockade,Unconventional Rydberg pumping,quantum information processing,Rydberg antiblockade,entanglement
更新于2025-09-23 15:23:52
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[IEEE 2018 International Carnahan Conference on Security Technology (ICCST) - Montreal, QC, Canada (2018.10.22-2018.10.25)] 2018 International Carnahan Conference on Security Technology (ICCST) - Microwave Quantum Radar: An Experimental Validation
摘要： We describe an experiment which comes very close to implementing a quantum radar based on entangled microwaves. A pair of entangled microwave beams are generated using a Josephson parametric amplifier (JPA) and measured by a pair of digitizers after amplification. We present a receiver operating characteristic (ROC) curve for the case where the signal power at the digitizers is ?83.84 dBm (corresponding to a JPA power output, before amplification, of ?148.26 dBm), as well as for a classically correlated source which attempts to approximate the covariance structure of the entangled JPA signals. The entangled signals are seen to be clearly superior to the classically correlated signals. Although the latter is still interesting from a noise radar perspective, this demonstrates that attempting to simulate entanglement with classical signals causes a measurable decrease in correlation. Our experiment validates the feasibility and desirability of a microwave quantum radar.
关键词： entanglement,Quantum radar,microwave,noise radar,correlation
更新于2025-09-23 15:23:52
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A hypothesis testing approach for communication over entanglement assisted compound quantum channel
摘要： We study the problem of communication over a compound quantum channel in the presence of entanglement. Classically such a channel is modeled as a collection of conditional probability distributions wherein neither the sender nor the receiver is aware of the channel being used for transmission, except for the fact that it belongs to this collection. We provide near optimal achievability and converse bounds for this problem in the one-shot quantum setting in terms of the quantum hypothesis testing divergence. We also consider the case of informed sender, showing a one-shot achievability result that converges appropriately in the asymptotic and i.i.d. setting. Our achievability proof is similar in spirit to its classical counterpart. To arrive at our result, we use the technique of position-based decoding along with a new approach for constructing a union of two projectors, which might be of independent interest. We give another application of the union of projectors to the problem of testing composite quantum hypotheses.
关键词： quantum hypothesis testing,one-shot information theory,position-based decoding,compound quantum channel,entanglement-assisted communication
更新于2025-09-23 15:22:29