Zheng-Hong Li

Quantum Secure Group Communication

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 efficient and securer. Particularly, in the security analysis, we introduce a new way of attack, i.e., the counterfactual quantum attack, which can steal information by “invisible” photons. This invisible photon can reveal a single-photon detector in the photon path without triggering the detector. Moreover, the photon can identify phase operations applied to itself, thereby stealing information. To defeat this counterfactual quantum attack, we propose a quantum multi-user authorization system. It allows us to precisely control the communication time so that the attack can not be completed in time.

Can quantum teleportation be achieved without the need for classical channel

It is somewhat challenging and confusing to the conventional mindset to say that teleportation can be achieved without classical channel. In this talk, I will show how quantum teleportation can be achieved without the need of classical channel. Our protocol does not require prearranged entangled photon pairs and Bell measurements. By utilizing quantum Zeno effect and couterfactuality, we can entangle and disentangle a photon and an atom by non-local interaction. The quantum information is completely transferred from atom to photon due to controllable disentanglement processes. The bonus here is that there is no need to cross check teleportation results via classical channels. It is worth mentioning that this protocol is a complement of the conventional quantum teleportation.

Quantum teleportation without classical channel

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 disentangling them by non-local interaction. Information is completely transferred from atom to photon with controllable disentanglement processes. More importantly, there is no need to confirm teleportation results via classical channels.

Time evolution of the Lamb shift

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 Lamb shift can then be separated into two parts: one is the time-independent shift due to the virtual photon exchange, and the other is the time-dependent shift due to the real photon emission. The time evolution depends on the nature of the coupling spectrum of the reservoir.