Shouvik Kanti Bhattacharya

PHY791 | 04.10.2014

“Active Cancellation of stray magnetic fields in a Bose-Einstein Condensation experiment”C. J. Dedman, R. G. Dall, L. J. Byron, and A. G. TruscottReview of Scientific Instruments 78, 024703(2007)

[1]

Phase transition of a graduate studentMoved to Omaha from Boston on the 10th

of August, 2013.Went through 3 different orientations in

the following 8 days (August 12- August 20, 2013).

Engaged in analytical solution of finding an optimum setup for cancelling magnetic fields and presented my work on October 30, 2013.

Bhattacharya 2

Bhattacharya 3

A common example of phase transition

Figure 1. The front yard of my residence, picture taken April 4, 2014, 8:42 am CST.

Bhattacharya 4

Sublimation/Evaporation

Figure 2. The front yard of my residence, picture taken April 4, 2014, 3:03 pm CST.

Bhattacharya 5

Let’s remind us about the Bose-Einstein condensateBose-Einstein condensation is a phase

transition.All bosons are at the ground state.The condensate occurs at a thermal

equilibrium.Superfluidity of helium and

superconductivity of an electron gas are caused by the Bose Einstein condensate.

6

Experimental Setup of the BEC

“The possibility of creating optical fields with many photons in a single mode of a resonator was realized with the creation of the laser in 1960. The possibility of creating a matter-wave field with many atoms in a single mode of an atom trap-the atomic equivalent of an optical resonator-was realized with the achievement of Bose-Einstein condensation(BEC) in 1995.” Wolfgang Ketterle[2]

Bhattacharya

Bhattacharya 7

History of the BEC Experiments

Figure 3. History of the BEC publications over time[2]

Bhattacharya 8

Controlling the Magnetic fields

A Stable magnetic field where the bosons are trapped in is a key requirement for many BEC and ultra cold atom experiments.

Examples: Quantum information processing, quantum simulation with qubits encoded in field sensitive atomic spin states.[3]

Bhattacharya 9

Controlling the Magnetic fields (cont.)

A complete shielding of the exterior magnetic field is also desired in some cases.

Experiment on the spinor condensates require to suppress the background magnetic field.[3]

Bhattacharya 10

Figure 4. Magnetic Noise [1]

Bhattacharya 11

What did they do?

An active system that responds to an abrupt change in magnetic field up to 3 kHz noise.

Their main objective was stabilizing the magnetic field by one part in ten thousand (10-10 T).

Bhattacharya 12

Some ways to shield a magnetic field

Shielding by a high permeable materialShielding by Eddy currentUsing 3-pairs of “active” Helmholtz

Coil

Bhattacharya 13

Figure 5. Experimental Design[1]

Bhattacharya 14

Integrator

Figure 6. A Schematic Diagram of an Integrator Circuit, Image courtesy: http://www.electronics-tutorials.ws/opamp/opamp_6.html

Bhattacharya 15

Integrating Vin

Figure 7.Image courtesy: http://www.electronics-tutorials.ws/opamp/opamp_28.html

Bhattacharya 16

Differentiator

Figure 8. A Schematic Diagram of a Differentiator Circuit, Image Courtesy: http://www.electronics-tutorials.ws/opamp/opamp_7.html

Bhattacharya 17

Differentiating Vin

Figure 9 Image courtesy: http://www.electronics-tutorials.ws/opamp/opamp_42.html

Bhattacharya 18

Result

Bhattacharya 19

Scope of work

Currently enrolled in PHY582 and hoping to finish the geomagnetic field suppression (passive system) experiment this semester.

Planning to enroll in PHY799 in summer and start making progress in the active magnetic field suppression.

20

Helmholtz Coils

1

2

Figure 10. A pair of Helmholtz coils. Image Courtesy: http://physicsx.pr.erau.edu/HelmholtzCoils/HelmholtzCoils.jpg

Bhattacharya 21

Radia

Figure 11. Changing the separation parameter and reporting associated magnetic field with it.

Bhattacharya 22

Acknowledgements

I would like to primarily thank to Dr. Jonathan Wrubel, Dr. Andrew Baruth, and Dr. Michael Nichols.

Dr. David Sidebottom and Dr. Kyle Watters

Nathan Holman and the AMO Research group at Creighton University (Spring 2014)

Bhattacharya 23

References[1] C. J. Dedman, R. G. Dall, L. J. Byron, and A. G. Truscott. 2007. Review of Scientific Instruments 78, 024703.

[2] Ketterle, Wolfgang. December, 1999. Physics Today.

[3] A Smith, B E Anderson, S Chaudhury, and P S Jessen, J. Phys. B: At. Mol. Opt. Phys. 44 (2011) 205001 (7ppm).

Bhattacharya 24

Questions

Figure 12. Bose Residency: Image Courtesy: http://upload.wikimedia.org/wikipedia/commons/2/22/Bose_Institute_-_Kolkata_7354.JPG