Entanglement and Bell’s Inequalities Lab
Freshman Quantum Optics Quiz
Name
(1)
What is the defining property of quantum entanglement?
a. measurements performed on the first particle gives reliable information about the
state of the second particle, only when the particles are close to each other.
b. rotating the coordinate system (basis) can change the state from entanglement to
the classical state.
c. measurements performed on the first particle gives reliable information about the
state of the second particle, no matter how far apart they may be.
d. the state of entanglement does not depend upon the coordinate (basis) rotation.
(2)
How did you create polarization entangled photons in your experiment?
a. Using a second harmonic generation from incident laser beam in birefringent
crystals.
b. Using a third harmonic generation from incident laser beam in birefringent
crystals.
c. Using an interference of two laser beams on the screen without any crystals.
d. Using a non-linear optical process, spontaneous parametric down conversion in
birefringent crystals
(3)
How did you prove in your experiment that you have entangled photons?
a. You should violate Bell’s Inequalities, and have fringe visibility greater than 0.71,
in coincidence count dependence on relative polarizer angle.
b. You should violate Bell’s Inequalities, and have fringe visibility less than 0.50, in
coincidence count dependence on relative polarizer angle.
c. You should have fringe visibility greater than 0.50, in coincidence count
dependence on relative polarizer angle.
d. Bell’s Inequalities should never be violated if you have quantum entanglement.
(4)
What is spontaneous parametric down conversion?
a. In this process one photon with a wavelength λ creates two photons with shorter
wavelengths with conservation of both energy and momentum.
b. In this process one photon with a wavelength λ creates two photons with larger
wavelengths with conservation of both energy and momentum.
c. In this process two photons with wavelengths λ1 and λ2 create two photons with
larger wavelengths with conservation of both energy and momentum.
d. In this process two photons with wavelengths λ1 and λ2 create two photons with
shorter wavelengths with conservation of both energy and momentum.
Entanglement and Bell’s Inequalities Lab
Freshman Quantum Optics Quiz
Page #2
Questions #5-8: A sketch of your experimental set up is shown below. Please label items #5-8,
using the following terms: one BBO crystal, two BBO crystals, detector, diode, interference
filter, polarizer, quartz plate. (You may use terms more than once.)
Question #6
Question #5
Question #7
Question #8
(5)
________________________
(6)
________________________
(7)
________________________
(8)
________________________
(9)
For what purpose do you need a quartz plate?
Filter
a. To compensate for the phase between the vertically and the horizontally polarized
components of the down converted photon as a result of different optical paths in
the birefringent crystals.
b. To increase the phase difference between the vertically and the horizontally
polarized components of the down converted photon as a result of different
optical paths in the birefringent crystals.
c. To make the output photons from the BBO crystals horizontally polarized.
d. To make the output photons from the BBO crystals vertically polarized.
Entanglement and Bell’s Inequalities Lab
Freshman Quantum Optics Quiz
Page #3
(10)
What are Bell’s inequalities? Can you calculate them for some classical objects?
a. Classical relations which, in the case of entanglement, are violated for some
angles of polarizers, they cannot be calculated in classical cases.
b. Bell’s Inequalities can be calculated only in the case of quantum mechanics.
c. Bell’s Inequalities are always violated in quantum mechanics (for all values of
polarizer settings).
d. Classical relations which, in the case of entanglement, are violated for some
angles of polarizers, they can be calculated in classical cases.
(11)
How did you calculate them in your Lab?
a. We need to carry out 16 measurements of coincidence counts for definite
polarizer angles at which the value of S has a maximum value.
b. We need to carry out 10 measurements of coincidence counts for definite
polarizer angles at which the value of S has a minimum value.
c. We need to measure cos2 dependence of the coincidence count on the relative
polarizer angle for 10 different settings with fringe visibility greater than 0.1.
d. We need to measure cos2 dependence of the coincidence count on the relative
polarizer angle for 16 different settings with fringe visibility greater than 0.5.
(12)
You know that you have the quantum state   H s H i  VsVi . How do you expect
count B to change as you rotate polarizer B from 0˚ to 360˚, but polarizer A is set for a
fixed angle ?
a. Single count B does change because the light is polarized.
b. Single count B depends upon the angle of polarizer A.
c. Single count B does not change because the light is not polarized.
(13)
If polarizer A was removed how would you expect the coincidence count to change as
you rotate polarizer B form 0˚ to 360˚?
a. Coincidence count changes as cos2 on the rotation angle of polarizer B.
b. Coincidence count does not change.
(14)
What is the difference between coincidence plot with no polarizer A and coincidence plot
with the polarizer A at =0?
a. In the case of polarizer A at α=0, the rotation of polarizer B changes the
coincidence count as cos2 dependence on the relative polarizer angle.
b. There will be no difference in the coincidence plots.
(15)
How do you define a fringe visibility?
a.
(Imaximum+Iminimum)/( Imaximum-Iminimum)
b. (Imaximum-Iminimum)/( 2Imaximum+Iminimum)
c. (Imaximum-Iminimum)/( Imaximum+Iminimum)
Entanglement and Bell’s Inequalities Lab
Freshman Quantum Optics Quiz
Page #4
(16)
What visibility should you have to violate Bell’s inequality?
a. Less than 0.71
b. Greater than 0.50
c. Greater than 0.71
d. Less than 0.50
(17)
How does a count rate of APD detector A (singles’ count rate) depend on the angle  of a
polarizer A and on the angle  of a polarizer B?
a. cos2(-)
b. does not depend upon  and 
(18)
What are the conditions for maximum and minimum coincidence count rates for setup
with two polarizers in front of each APD? (Please provide your answer in the space
provided below.)