Apparatus

Apparatus

The light source for the experiment was a tube with a lightbulb inside it. The end of the tube was covered by an Edmund Optics EO56097 bandpass filter and a 15 µm slit. In our setup, the single slit separation is 34 μm, the distance between the double slits was 500 μm, and the bandpass filter allowed a wavelength of about 546±5 nm to pass through. The distance between the single and double slits was 47.5 cm. The light beam was then sent into an initial polarizing filter oriented at a 45 degree angle from the quantum markers. Afterwards, the light traveled through a double slit with slits 80 µm wide and 500 µm apart.

In the first setup, the light traveled to a Hamamatsu H6240-01 photomultiplier tube (PMT) which was mounted on a Thorlabs MTS50-Z8 motorized translation stage. The PMT detected incident photons and outputted the number of events counted over a set period of time, which gave the number of events counted per second which is proportional to the intensity. The motorized translation stage moved the PMT along a path perpendicular to the incoming interference pattern, so that the angle of the light could be determined from the PMT readings. The PMT had a 20 µm slit covering it to ensure that the intensity data was taken from a single point along the diffraction pattern. The motorized translation stage and PMT were connected to a computer via a National Instruments CB-C68LP Data Acquisition Card (DAQ) and controlled using a LabView program to take measurements. The PMT and light source were powered via an Agilent E3630A power supply. The motorized translational stage was powered by a Thorlabs motor controller and external power supply.

The second setup was the same same except the quantum markers were placed over the exit of each of the slits that made up the double slit.

The third setup was the same as the second setup except the quantum eraser was placed after the quantum markers.

The following pictures show the setup inside the black box:

Beginning of Setup. From bottom to top: Light source with bandpass filter, initial slit, initial polarizer, double slit.

End of Setup: From top to bottom: Double slit and quantum markers (both hidden by eraser), quantum eraser, PMT and Translation Stage

The entire experiment was conducted in this black box. The power supply is on top. It provided 5V to the PMT and 6V to the light source. The BNC cables connected to the box power and carry the signals from the translation stage and PMT. There is an additional BNC cable on the other side of the box that carries power to the light source.