Suppressing decoherence in entangled qubit registers via repeated joint measurements

Qiao-Yun Tan, Lin Wang, Jinxiang Li +2 more

O. M. Konovalenko, Z. А. Maizelis

We propose a method to suppress decoherence in entangled systems by applying the series of joint measurements. While the standard Quantum Zeno Effect approach can only compensate for the slow enough Hamiltonian dynamics of the quantum system, the characteristic frequencies of the thermal bath contacting system may be greater than the maximal achievable frequencies of measurements. In this case, they cannot cancel out non-Hamiltonian evolution leading to the decoherence. We propose to use entanglement between the qubits of a quantum register to mitigate the negative effects of the interaction with the thermal bath, even with the lower frequencies of measurement. We show that even though this protocol does not lead to a complete freezing of the initial state, it still allows effective preservation of the entanglement in the system.

Mohammad Mehdi Sahrapour, Nancy Makri

David S. Simon, Shuto Osawa, Alexander V. Sergienko

Linear-optical systems can implement photonic quantum walks that simulate systems with nontrivial topological properties. Here, such photonic walks are used to jointly entangle polarization and winding number. This joint entanglement allows information processing tasks to be performed with interactive access to a wide variety of topological features. Topological considerations are used to suppress errors, with polarization allowing easy measurement and manipulation of qubits. We provide three examples of this approach: production of two-photon systems with entangled winding number (including topological analogs of Bell states), a topologically error-protected optical memory register, and production of entangled topologically-protected boundary states. In particular it is shown that a pair of quantum memory registers, entangled in polarization and winding number, with topologically-assisted error suppression can be made with qubits stored in superpositions of winding numbers; as a result, information processing with winding number-based qubits is a viable possibility.

O. M. Konovalenko, Z. А. Maizelis

We apply the multiple, equally spaced in time, weak measurements, to the two-qubit entangled system to decrease the rate of its decoherence, i.e., to prevent the decrease of the off-diagonal elements. The scheme is similar to the Quantum Zeno Effect, but differs by the frequency of the measurements. While the conventional Quantum Zeno Effect assumes rapid measurements which mitigates the Hamiltonian dynamics, the proposed method makes use of entanglement between the qubits to decrease the decoherence rate. We will show that it allows us to partially suppress the decoherence in the case of Lindblad evolution.

Anonymous