• ABSTRACT – HUMAN BELL TEST: PUSHING THE LIMITS OF SCIENCE

Quantum mechanics predicts that objects can share a connection stronger than anything we experience in our everyday experiences, something that is called quantum entanglement. Even if the objects are separated by a great distances, independent measurements on them will show they are correlated in ways that cannot be explained by classical physics or intuitions. These properties, which Einstein termed “spooky actions at a distance,” can be tested in an experiment known as a Bell test. In 2015, NIST was one of the first groups to carry out a complete test of Bell theorem using quantum states of light, and conclusively show the presence of this “spooky action.” However, in that experiment the decisions about how to carry out the measurements were made by random numbers generated from different physical processes. There still remain questions about whether human can have any influence on such quantum decisions. We will be repeating our experiment from 2015, but this time using random numbers provide by you. You will get to directly control our experiment, and we will be able to see if the results using human inputs differ from those using random numbers from physical sources. 

• FACTS
  • We create 400,000 entangled photons per second to use in our experiment.
  • 35 researchers from ten institutes in North America and Europe came together to help us build our first version of the loophole-free Bell test.
  • To make our experiment happen, we need to use fast devices that can measure our photons. These devices can be switched on in only a few billionths of a second.
  • During the three months we conducted our first Bell test in 2015 (not using human generated random numbers), one of our scientists got married. Talk about entanglement!
  • We use the world”s best low-light camera to detect our photons. These detectors are made out of superconductors, and must be operated at less than a degree above absolute zero.
  • To perform the experiment, we must squeeze our photons into a tiny cable made of glass that is only a few millionths of a meter in diameter. Getting the photons to hit this tiny target is a feat of quantum archery.

 

• QUOTE

“In 1964 John Bell profoundly changed the way we think about quantum mechanics. Bell”s theorem lies at the very heart of quantum mechanics, philosophy, and a new class of technological breakthroughs based on quantum mechanics.”

1. Name of Lab:

The Bell Test Machine (or NIST Bell Test Site)

2. Team:

Krister Shalm, Martin Stevens, Omar Magana Loaiza, Thomas Gerrits, Scott Glancy, Peter Bierhorst, Emanuel Knill, Richard Mirin, Sae Woo Nam (PI)

3. Organization:

National Institute of Standards and Technology (NIST)

4. City:

Boulder, Colorado

5. GPS coordinates of the experiment:

Latitude: 39.994798 | Longitude: -105.262907 Altitude: 1653 meters

6. Name of the experiment:

The Bell Test Machine

7. Target Bell inequality and experimental result obtained:

CH (Clauser-Horne) inequality: local realism implies J≤0. We obtained a value for J of (1.65 ± 0.20) x 10^(-4), which corresponds to a violation of the inequality by more than 8.7 standard deviations.

8. What did the experiment test?

We performed a test of Bell’s inequalities that simultaneously closed the locality and detection loopholes. Instead of closing the freedom of choice loophole using physical random number generators, we instead used the random choices from human participants. We wanted to see if there was a difference between the results of a Bell test where humans had some agency in making the choices at Alice and Bob versus physical random number generators. We did not observe any noticeable difference, and the human inputs were still able to violate a Bell inequality.

9. Physical system used:

We used non-maximally entangled photon pairs generated from the process of parametric downconversion.

10. Degree of freedom measured:

We entangled and measured the polarization degree of freedom of the photons.

11. Rate of bits consumed & total number of bits We did not do the experiment live. Instead we collected and used 81,119,980 bits. Then we ran our experiment at a rate of 100,000 trials/s, and consumed our bits at a rate of 200,000 bits/s, because Alice and Bob each use one bit per trial.
12. What was the use of the bits of the Bellsters

In our experiment, we measured a property of light known as polarization. As light travels through space it wiggles in a particular direction. This direction is known as its polarization. To measure the polarization direction of light, we use a device called a polarizer. Polarizers are typically found in sunglasses. Take a pair of polarized sunglasses and look at a computer screen (that emits polarized light). By rotating the sunglasses, you should see the screen either brighten or dim. In our experiment, we use a sophisticated version of the polarizers typically found in sunglasses that is capable of rotating 100,000 times every second! Every random bit that Bellsters provided caused one of the polarizers in our experiment to rotate to a given position.

13. How long did the experiment take?

Our experiment ran for nearly 7 minutes. In that time we used over 80 million random bits that the Bellsters supplied us. We performed our experiment 100,000 times/second. We started our experiment at 11:09 PM (Local time in Boulder) on November 30th, and finished 7 minutes later.

14. Did you use all the bits in real time?

Because our system is designed to run at high speeds, we needed to first collect as many random bits as we could. Over the course of the Big Bell test day, we stored over 80 million of the bits that came in. Once we had stockpiled enough bits, we ran our experiment. In less than 7 minutes, we managed to use up all the bits that over 100,000 Bellsters supplied to us throughout the day!

15. Distance between Alice and Bob

Alice and Bob were 187 m apart. The distance between the photon source and Alice is 133.4 +/- 1.0 m, and the distance from the source to Bob is 129.2 +/- 1.0 m. We say that the measurement is complete when, after a photon is detected at either Alice or Bob, the amplified electrical signal reaches the input of the time tagger that records the outcome. We do not satisfy the freedom of choice loophole as we use bits from human participants that are not “fresh” (the light cone from their creation events intersected many hours prior). Instead, we guard against the possibility that when the fast polarizers (Pockels cells) switch states at Alice, the large voltages involved in the process could influence in a correlated manner Bob’s measurement device. In this case, we satisfy the locality constraints by at least 294.4 +/- 3.7 ns.