Listen to the vacuum

1 · Say what was seen

Beginner

What did the experiment at the European X-ray laser produce?

The first X-ray photons deflected by light No signal, hence an upper limit Scattering stronger than the quantum prediction

2 · Count the campaigns

For the whole campaign of 2,751 collisions, the simulation predicts 0.0008 signal photon in the flipped channel.

Intermediate

How many identical campaigns would it take to expect a single signal photon?

About 1,250 About 70,000 About 56

3 · Choose the channel for the limit

In the unchanged-polarization channel (∥), the expected signal would be about 13.4 times larger than in the flipped channel (⊥). Yet the limit is drawn from the ⊥ channel.

Expert

Why?

Because the ∥ channel was not recorded Because the signal would be smaller there Because the ∥ channel receives thousands of probe photons on every shot

4 · Predict the ratio of the channels

For the response of the vacuum, quantum electrodynamics predicts a ≈ 4 and b ≈ 7. The ratio of the signals in the two channels is N⊥ / N∥ ≃ (a − b)² / (a + b)².

Expert

What value of this ratio should a future measurement find?

1: as much signal in each channel About 0.074 About 13.4

Vacuum heard

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