1. Single Photon Interference Jeff, Jacob, Bryce, Edward, and Julie

2. Young’s Double Slit Experiment YAY!

3. What is it?  First conducted in 1801 by Thomas Young  Light passed through a barrier with two slits (before it usually passed through a single slit to make the light coherent)  The light diffracted through each slit  Created interference pattern  In order to interfere the light that passes through the slit must be of the same frequency and polarization and it must be coherent

5. Particles vs. Waves Particle  If light acts as a particle, only two slits will appear on the screen Wave  The light will diffract and interfere, making many fringes

6. Why is this important?  This proves light acts not only as a particle, but also as a wave!

7. Equations for the Fringes

8. Many Photon Interference Acquisition Time:.1 sec Attenuation: 3 optical depths Amplification: x1

9. Single Photon  When a single photon is used, wave interference is still present  It is impossible for a photon to act as a wave as it is can only go through one slit  If one slit is blocked, there is no interference

10. Energy of a Single Photon

11.  Power of 1 photon per meter  P=9.421 ∗ 10 −11 W  The power of our laser is  P=9.1 ∗ 10 −7 W  So we use 3 optical depths to attenuate the beam to single photon energy levels.

12. Single Photon Interference Acquisition Time:.1 sec Attenuation: 3 optical depths Amplification: x100

13. Single Photon Interference Acquisition Time:.1 sec Attenuation: 3 optical depths Amplification: x200

14. Single Photon Interference Acquisition Time: 1 sec Attenuation: 3 optical depths Amplification: x100

15. Interferometry Mach-Zehnder Interferometer

16.  Power of 1 photon per meter  P=9.421 ∗ 10 −11 W  The power of our laser is  P=6.17 ∗ 10 −5 W  So we use 5 optical depths to attenuate the beam to single photon energy levels.

17. Strong field Acquisition Time:.1sec Attenuation: 5 optical depths Amplification: x100

18. Single Photon Acquisition Time:.1 sec Attenuation: 5 optical depths Amplification: x100

19. Single Photon – Horizontal Polarization Blocked Acquisition Time:.1 sec Attenuation: 5 optical depths Amplification: x100

20. Single Photon – Vertical Polarization Blocked Acquisition Time:.1 sec Attenuation: 5 optical depths Amplification: x100

21. Important Observations  When path of photon is unknown, fringes are observed  When path of photon is known, fringes are not observed

22. Summary  Young’s Double Slit Experiment  Fringes were observed under high intensity, as well as with only a single photon.  Interferometer  Fringes were observed under high intensity as well as with only a single photon.  When either path of the interferometer was blocked, fringes were not observed.

23. What Problems Did We Encounter? Single Photon Interference Acquisition Time:.1 sec Attenuation: 5 optical depths Amplification: x100

25. Conclusion  Single photons behaved the same way as the high intensity beam.  In the double slit experiment, the single photon appeared to interfere with itself – going through both slit simultaneously.  In the interferometer the single photon appeared to take both paths simultaneously – blocking a path removed interference fringes.

26. Sources  http://www.studyphysics.ca/newnotes/20/unit04_ligh t/chp1719_light/lesson58.htm http://www.studyphysics.ca/newnotes/20/unit04_ligh t/chp1719_light/lesson58.htm  http://dev.physicslab.org/asp/applets/double slit/default.asp http://dev.physicslab.org/asp/applets/double slit/default.asp  http://physics.about.com/od/lightoptics/a/do ubleslit.htm http://physics.about.com/od/lightoptics/a/do ubleslit.htm  http://www.physics.brown.edu/physics/demo pages/Demo/modern/demo/7a5520.htm http://www.physics.brown.edu/physics/demo pages/Demo/modern/demo/7a5520.htm  The book – Seeing the Light