Advanced Labs
Here at the University of Minnesota, students and staff of MXP perform several advanced and detailed labs. Listed below are the advanced projects with a brief summary and a link to a dedicated page including a detailed explanation of the setup used as well as results.
Single Photon Quantum Interference
The Quantum Interference lab is designed to confirm the existence of photons using a statistical approach. Generally, two single entangled photons are created and forced to interfere. The first part of this lab is confirming that you are indeed working with single photons. By entangling photons using a BBO crystal and maximizing an anti-correlation parameter between two independent detectors, one confirms the existence and obtains the isolation of single photons. After this is accomplished, the experimenter can choose to do a variety of tests. The Mach Zehnder interferometer setup and Hardy's Test of Local Realism are two common choices described on pages of their own.
Hong Ou Mandel
The Hong Ou Mandel lab is similar in scope to the Single Photon Quantum Interference lab, however uses two photons to prove that two separate photons interfere with each other. Two single entangled photons are created and forced to interfere. The first part of this lab is confirming that you are indeed working with single photons. By entangling photons using a BBO crystal and a fiber optic setup, and maximizing an anti-correlation parameter between two independent detectors, one confirms the existence and obtains the isolation of single photons. After this is accomplished, the experimenter will set up two separate paths for the paired photons to travel and find the "HOM dip," or the point where the photons along the two paths maximally destructively interfere.
Experimental setup used for a Mach-Zender Interferometer using a single photon beam.
Speckle Interferometer
Speckle interferometry is the use of a diverging beam to make two speckle patterns that are subtracted in order to measure small changes in objects. Common uses include measure the vibrational modes of bulk metals and other materials as well as characterizing dynamical properties of fluids through a change in their index of refraction. The experiment described on this site is using a speck interferometer to characterize the vibrational modes of a thin aluminum plate and measure the change of the plate's surface when bent a few microns in the center.
Speckle interferometry pattern using a HeNe Laser striking an aluminum plate
Mössbauer Effect
The Mössbauer experiment is one where the transition levels of excited nuclei are found and classified. Nuclei experience the Zeeman effect just like electrons do, when in a magnetic field. Along with the Zeeman effect, the energy levels of nuclei experience an isomer shift (a small change resulting from Coulomb interactions of different isotopes) and a Quadrupole splitting. Shown to the right is the spectrum of Fe2O3. The dips correspond to the absorption energies of the nucleus.
Results of Moessbauer Experiment analyzing Iron Oxide
Quadrature Michelson Interferometer
The quadrature interferometer is a device used to measure small displacements through the interference of light waves. The quadrature interferometer differs from a regular interferometer by utilizing two axis of polarization to decipher directional information. This lab hones skills like optical alignment and can be used to investigate many different phenomena. The measurement most often made in this lab is the start/stop inchworm-like motion of a rod struck at one end.
Quadrature Interferometer setup and diagram.
Saturated Absorption Spectroscopy
Saturated absorption spectroscopy is an advanced non-linear spectroscopy method used to eliminate Doppler broadening in the energy spectrum. This is accomplished using two important themes. First, there are two counter-propagating beams essentially to "see" the gas from both directions and cancel out movements along that axis. Second, the gas is saturated to change the spectrum from an absorption profile to an emission one and to guarantee the dominant population is the lowest or ground state. Saturated absorption spectroscopy is widely used in today's physics labs but our lab focuses on using it to characterize the transitions of the noble gas Rubidium.
Intensity of beam using saturated absorption spectroscopy
Surface Plasmon Resonance
Surface plasmon resonance is a technique most commonly used to measure the index of refraction of thin films adsorbed onto metal. More recently this technique has been adopted to enhance Ramen spectroscopy. The setup used in our lab is the Kretchmann setup consisting of a prism on top of the adsorption/metal