Longer-Baseline Telescopes Using Quantum Repeaters

We present an approach to building interferometric telescopes using ideas of quantum information. Current optical interferometers have limited baseline lengths, and thus limited resolution, because of noise and loss of signal due to the transmission of photons between the telescopes. The technology of quantum repeaters has the potential to eliminate this limit, allowing in principle interferometers with arbitrarily long baselines.

Figure 1

Basic setup of a direct-detection interferometer. In the arrangement pictured, light travels an additional distance $b\sin \theta$ to reach telescope $L$ rather than telescope $R$. For light with wavelength $\lambda$, the extra distance imposes a phase shift $\varphi =(b\sin \theta )/\lambda$ at telescope $L$ relative to telescope $R$.

Figure 2

Performing an interference measurement between two telescopes using an entangled state emitted from a central entangled photon source (EPS).

Figure 3

Creating shared entanglement. (a) shows the simplest scenario: pass one single photon through a beam splitter and send the resulting entangled modes to the receivers. (b) In a quantum repeater, a series of quantum relays entangles several entangled photon pairs via a Bell-state measurement (BSM), and uses entanglement distillation (ED) to extract high-quality entanglement between distant receivers.