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Constraints on Gaussian Error Channels and Measurements for Quantum Communication
Alex Kwiatkowski1,2, Ezad Shojaee1,2, Sristy Agrawal1,2
1National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Physical Review. A
|November 15, 2023
Summary
Independent Gaussian error channels can make joint Gaussian measurements unusable for quantum communication tasks like entanglement swapping. This study identifies specific error channel conditions that lead to separable measurements, hindering quantum protocols.
Area of Science:
- Quantum Information Science
- Quantum Communication
- Quantum Optics
Background:
- Joint Gaussian measurements are crucial for quantum communication protocols such as continuous-variable teleportation and entanglement swapping.
- Real-world quantum systems often suffer from independent Gaussian error channels affecting measurements.
Purpose of the Study:
- To identify conditions under which independent single-mode Gaussian error channels render all joint Gaussian measurements separable.
- To determine the impact of these separable measurements on quantum communication protocols.
Main Methods:
- Analysis of independent single-mode Gaussian error channels acting on two quantum systems (modes A and B) prior to joint Gaussian measurement.
- Derivation of the criteria for separability of Gaussian measurements under specific error channel models, including loss and added noise.
Main Results:
- The study determines the exact set of pairs of independent Gaussian error channels that result in separable joint Gaussian measurements.
- A specific condition is found for loss and added noise channels: separability occurs if the sum of loss and noise parameters (l_A + l_B + n_A + n_B) is greater than or equal to 1.
Conclusions:
- Certain combinations of independent Gaussian error channels can render joint Gaussian measurements inseparable, thus unsuitable for entanglement swapping or teleportation.
- Understanding these error channel limitations is vital for the practical implementation of advanced quantum communication protocols.
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