Zheng-Hong Li

Shanghai University | SHU · Department of Physics

Cat states, as an important resource in the study of macroscopic quantum superposition and quantum information applications, have garnered widespread attention. To date, preparing large-sized optical cat states has remained challenging. We demonstrate that, by utilizing interaction-free measurement and the quantum Zeno effect, even a fragile quantu...

A deterministic preparation method for large-amplitude optical Schr\"odinger-cat state is proposed. The key ingredient is to entangle an atom buried in a single-side cavity with a large-amplitude coherent light pulse. To achieve this purpose, a multiple reflection Michelson interferometer is used. The light pulse can go back and forth inside the in...

The direct counterfactual quantum-communication protocol involving double-chained Mach-Zehnder interferometers requires a single-photon input. Here, we show that even with multiphoton light sources, including a strong coherent light source as input, the counterfactual communication can be achieved with success probability approaching unity in the i...

It is of fundamental interest in controlling the light–matter interaction for a long time in the field of quantum information processing. Here, we explore a model by coupling a giant atom with the dynamically-modulated coupled-resonator waveguide and find the bound state, where the light shows the localization effect and the atomic decay into reson...

The direct counterfactual quantum communication protocol involving double chained Mach-Zehnder interferometers requires a single photon input. Here, we show that even with multiphoton light sources, including a strong coherent light source as inputs, the counterfactual communication can be achieved with success probability approaching unity in the...

We study a theoretical model where light transports along a dynamically-modulated coupled-resonator waveguide interacting with a giant atom, and find a bound state where photon is localized and excited atom exhibits a subradiant decay.

The ability to communicate secure information is of utmost importance. Hitherto, this has been achieved within the domain of classical communication by capitalizing on mathematical complexity. However, classical communication has limitations of both speed and security. As a result, the focus has shifted towards quantum physics for the implementatio...

We present how basic logic gates including nand, nor, and xor gates can be implemented counterfactually. The two inputs (Bob and Charlie) and the output (Alice) of the proposed counterfactual logic gate are not within the same station but rather separated in three different locations. We show that there is no need to prearrange entanglement for the...

Trojan horse attack is a common eavesdropping strategy which can attack various quantum secure communication systems. Its basic idea is to send auxiliary photons into a legitimate communicator's apparatuses and steal information by analyzing the reflected photons. In this paper, we consider a different kind of Trojan horse attack, the so-called cou...

We present how basic logic gates including NAND, NOR and XOR gate can be achieved counterfactually. The inputs and outputs of these counterfactual logic gates are not within the same station but rather separated at different locations. We show that there is no need to pre-arrange entanglement for the proposed counterfactual logic gates, and more im...

We show that two unknown quantum states, either pure or mixed, can be bidirectionally “teleported” counterfactually. In the process of information exchange, there is no physical particle traveling between two communicators. Unlike conventional quantum teleportation, our protocol requires neither prearranged entangled pairs nor Bell measurements. We...

We propose a quasi-counterfactual quantum swap gate for exchanging Alice’s unknown photon state and Bob’s unknown atomic state under the condition that only Alice’s photon may appear in the transmission channel between Alice and Bob, while the probability of the existence of photon in the transmission channel is controllable and can tend to zero. U...

We propose a quantum secure group communication protocol for the purpose of sharing the same message among multiple authorized users. Our protocol can remove the need for key management that is needed for the quantum network built on quantum key distribution. Comparing with the secure quantum network based on BB84, we show our protocol is more effi...

For the first time, we show how quantum teleportation can be achieved without the assistance of classical channels. Our protocol does not need any pre-established entangled photon pairs beforehand. Just by utilizing quantum Zeno effect and couterfactual communication idea, we can achieve two goals; entangling a photon and an atom and also disentang...

We address criticisms made in the preceding Comment by Vaidman regarding our claims of counterfactuality of transmission of a quantum state in our recent work.

We show that an unknown quantum state can be transferred with neither quantum nor classical particle traveling in the transmission channel. Our protocol does not require prearranged entangled photon pairs and Bell measurements. By utilizing quantum Zeno effect and counterfactuality, we can entangle and disentangle a photon and an atom by nonlocal i...

We propose a protocol for direct quantum communication between two parties (Alice and Bob) which is achieved by controlling the phase of the signal photon. Without imperfection and noise, Alice's two detectors always click with unit probability according to Bob's different decisions. The probability of detecting a photon in the transmission channel...

DOI:https://doi.org/10.1103/PhysRevLett.112.208902

In reply to Vaidman's Comment [arXiv:1304.6689], we show that his claim that our Protocol for Direct Counterfactual Quantum Communication [PRL 110, 170502 (2013), arXiv:1206.2042] is counterfactual only for one type of information bit is wrong.

We present an analysis of a nested Mach-Zehnder interferometer in which an ensemble of identical pre- and postselected particles leaves a weak trace. A knowledge of the weak value partially destroys the quantum interference. The results, contrary to some recent claims [Vaidman, Phys. Rev. A 87, 052104 (2013)], are in accordance with the usual quant...

We present an analysis of a double Mach-Zehnder interferometer in which an ensemble of identical pre- and postselected particles leave a weak trace. A knowledge of the weak value partially destroys the quantum interference. The results, contrary to some recent claims, are in accordance with the usual quantum mechanical expectations.

It has long been assumed in physics that for information to travel between two parties in empty space, "Alice" and "Bob," physical particles have to travel between them. Here, using the "chained" quantum Zeno effect, we show how, in the ideal asymptotic limit, information can be transferred between Alice and Bob without any physical particles trave...

The third level has great influence on the time evolution of the spontaneous decay from the excited state, when the counter-rotating terms are taken into account. The influence in the cascade-type and V-type three-level systems is investigated for two initial states, excited from the ground states of the whole system (atom plus vacuum modes) and fr...

We study the quantum interference in spontaneous emission with the inclusion of counterrotating terms and energy shifts. The energy shifts come from the emission and then reabsorption of virtual photons as well as the real photon emission. We show that the quantum interference resulting from the energy shifts has significant influence on the effect...

The time evolution of the Lamb shift that accompanies the real photon emission is studied for the first time (to our knowledge). The investigation of the explicit time dependence of the Lamb shift becomes possible because the self-energy of the free electron, which is divergent, is subtracted from the Hamiltonian after a unitary transformation. The...

A unitary transformation method is used to investigate the dynamic evolution of two multilevel atoms, in the basis of symmetric and antisymmetric states, with one atom being initially prepared in the first excited state and the other in the ground state. The unitary transformation guarantees that our calculations are based on the ground state of th...

The influence of the modification of the free vacuum on the quantum Zeno and anti-Zeno effects, as well as the Lamb (energy) shift of a multilevel atom, is studied. A unitary transformation method has been used to include the counter-rotating terms and to obtain the ground state of the whole Hamiltonian. The anti-Zeno effect is recovered if the mod...

The spontaneous decay of a multilevel atom interacting with the electromagnetic field in free space is investigated with a unitary transformation method, which is introduced in order to include all rotating and counter-rotating terms in the Hamiltonian. By using the ground state of the total Hamiltonian, the evolution of the effective decay rate an...

The two-photon transition for a two-level atom interacting with a single-mold electromagnetic field has been investigated. The initial coherent states with time-varying frequency are considered. The effects of the frequency modulation in sinusoidal form on the atomic population inversion and the squeezing properties of the atom and field are studie...