Quantum amplification in the presence of decoherence

Ankit Tiwari, Cecilia Cormick, Christian Arenz

We consider the amplification of bosonic interactions through parametric control that implements squeezing along orthogonal quadratures. We show that bosonic interactions described by certain classes of quadratic and quartic Hamiltonians can be enhanced in this way while simultaneously overcoming noise and decoherence. In general, the amplification method enhances both desired and undesired interactions present in the system. Depending on the case, however, detrimental processes can be less amplified than the desired couplings. We leverage this observation to improve the fidelity for preparing Bell-type entangled states between two bosonic modes in the presence of noise and losses. We also investigate noise models for which the protocol either fails or partially achieves a loss-tolerant state preparation speedup. Our work facilitates faster preparation of complex quantum states and implementation of entangling gates in the presence of decoherence mechanisms.

Chun-yao Liu, Zheng‐Wen Long, Qi-Liang He

We investigate the amplification of the genuine tripartite nonlocality (GTN) and the genuine tripartite entanglement (GTE) of Dirac particles in the background of a Schwarzschild black hole by a local filtering operation under decoherence. It is shown that the physically accessible GTN will be completely destroyed by decoherence, and the local filtering operation can cause the physically accessible GTN to be generated in the system coupled with the environment, which has not been discovered before and is beneficial for quantum information processing. Furthermore, we also find that the physically accessible GTE approaches a stable value in the limit of infinite Hawking temperature for most cases, and the nonzero stable value of GTE can be increased by performing the local filtering operation, even in the presence of decoherence. In particular, if the decoherence parameter p is less than 1, the “sudden death” of GTE will take place when the decoherence strength is large enough. Finally, we have shown that physically inaccessible GTE can be enhanced with the operation of the local filter, whereas inaccessible GTN are not allowed to occur in the presence of decoherence.

H. T. Quan, Zhijun Song, Xiaobao Liu +2 more

Jaewoo Joo, Matthew Elliott, Daniel K. L. Oi +2 more

Perfect deterministic amplification of arbitrary quantum states is prohibited by quantum mechanics, but determinism can be achieved by compromising between fidelity and amplification power. We propose a dynamical scheme for deterministically amplifying photonic Schrödinger cat states, which show great promise as a tool for quantum information processing. Our protocol is designed for strongly coupled circuit quantum electrodynamics and utilizes artificial atomic states and external microwave controls to engineer a set of optimal state transfers and achieve high fidelity amplification. We compare analytical results with full simulations of the open, driven Jaynes–Cummings model, using realistic device parameters for state of the art superconducting circuits. Amplification with a fidelity of 0.9 can be achieved for sizable cat states in the presence of cavity and atomic-level decoherence. This tool could be applied to practical continuous-variable information processing for the purification and stabilization of cat states in the presence of photon losses.