Wednesday, May 31, 2017


After the somewhat grueling 24-hour flight from Baton Rouge to Okinawa, I arrived late Tuesday night local time. Given that I had just spent two weeks in Shanghai, which is only an hour different than here, I'm not jet lagged! Having missed dinner all together Tuesday evening, I raced down to the OIST cafeteria for breakfast Wednesday morning, which consisted of three slices of pizza, a boiled egg, a glass of orange juice, and a double-shot latte. I may not be regular again until the next Clinton administration.

At 9AM sharp Prof. Síle Nic Chormaic's postdoc, Dr. Jinjin Du, gave us a short tour of the local part of the island and then we had lab tours and discussions from 11AM until about 12:30PM, another break for pizza and coffee, and then back for more discussion on the transfer of higher-order modes of light through fibers to couple nonlinearly with neutral atoms — does LSU have a theory for that!

The Prof. Irina Novikova, my long-time collaborator gave the experimental version of our collaboration in a nice seminar on the generation of multimode squeezed light in rubidium vapor. 

I will give the theory version of our collaboration tomorrow in a not so nice seminar. Next Síle (pronounced "Shelia" will be taking us out for local cuisine — Italian / Spanish / French food with local ingredients. Then tomorrow we do it all over again! 

My lovely little cottage on a cliff.

View from my back porch.
What have you done with my pet bottle, Cecil!?

A used TOKAMAK that doubles as a tunnel?
Eggxactly what the doctor ordered?
OIST on approach.

OIST koi pond.

Left to right: Alexandre Akoulchine, Irina Novikova, JinJin Du.
"You can't take a photo of a hole — it is an absence of matter!"
A relic from 1947?

I can't define a photon, but I know one when I see one.

Laser-cooled Rubidium atoms interact with an optical fiber.

OIST PhD Student, Thomas Nieddu, explains why it is all very "cool".

Irina regales us with tales of experiments for multimode squeezed light

View from my office.

Tuesday, May 30, 2017

Fundamental precision limit of a Mach-Zehnder interferometric sensor when one of the inputs is the vacuum

Masahiro Takeoka, Kaushik P. Seshadreesan, Chenglong You, Shuro Izumi, Jonathan P. Dowling
In the lore of quantum metrology, one often hears (or reads) the following no-go theorem: If you put vacuum into one input port of a balanced Mach-Zehnder Interferometer, then no matter what you put into the other input port, and no matter what your detection scheme, the sensitivity can never be better than the shot noise limit (SNL). Often the proof of this theorem is cited to be in Ref. [C. Caves, Phys. Rev. D 23, 1693 (1981)], but upon further inspection, no such claim is made there. A quantum-Fisher-information-based argument suggestive of this no-go theorem appears in Ref. [M. Lang and C. Caves, Phys. Rev. Lett. 111, 173601 (2013)], but is not stated in its full generality. Here we thoroughly explore this no-go theorem and give the rigorous statement: the no-go theorem holds whenever the unknown phase shift is split between both arms of the interferometer, but remarkably does not hold when only one arm has the unknown phase shift. In the latter scenario, we provide an explicit measurement strategy that beats the SNL. We also point out that these two scenarios are physically different and correspond to different types of sensing applications.

Cite as: arXiv:1705.09506 [quant-ph]

Saturday, May 27, 2017


It's Saturday afternoon in Shanghai and my flight to Dallas boards in an hour. Only 12 hours it looks. Great excitement and fun and research with Tim Byrnes at NYU Shanghai. Here is our farewell shot. 

We celebrate with sparkling grape juice!

When I arrived on Monday we made a to-do list and then when we pulled it up on Friday we could tick off many things, delete many things, and add new things. All in all in this two-week period we have either submitted or resubmitted or nearly submitted five refereed publications. Two per day!

Here are some parting shots of the NYU gang. 

Dr. Chandrasekar apparently has no limits.


The Qubit Caballero discovers inside is sticky rice filled with either sweet red-bean paste or savory meat paste.
It's Schrödinger's Dumpling!

Traditional last night dinner at the Wolf Factory.
Lamb shishkabops!

Last elevator ride. But where's Chenyu?

THERE she is!

Home in Baton Rouge for 24 hours then off AM Monday on a 24 hour flight to Okinawa where I'll visit OIST and the group of  fellow Irish person Sile Nic Chormaic (Sheila) along with our long-time collaborator, Irina Novikova at William & Mary College. We will discuss orbital angular momentum states of light interacting with nonlinear optical media! 

OIST! Rhymes with MOIST?
Stay tuned for #WIDOMSUMVAC — OKINAWA: DAY 1!

Thursday, May 25, 2017


We are coming into the home stretch and have at least two theory papers in the works with our collaborators for USTC as co-authors. One Physical Review A article on quantum metrology has been resubmitted. One Physical Review Letters article we are discussing the response to the referees. 

Responding to the referees.
Tomorrow is my last day and we'll hammer out a game plan for modelling the USTC boson-sampling experiment. Collaborations between Louisiana State University, NYU Shanghai, and the University of Science and Technology of China are underway! Alas I depart 4:10PM SAT27MAY Shanghai time for my 20 hour flight to Baton Rouge via Dallas. I arrive at the DFW airport at 4:45PM SAT27MAY — only 35 minutes after I took off! Gotta love that International Dateline! Then I get about 24 hours rest before I board my flight 9:03AM MON29MAY in Baton Rouge to begin my 24-hour flight to Okinawa!

A recap in photos of yesterday and today where I have commandeered the camera to show we actually work all day!

I knight you Sir
José Eduardo Cejudo Grano de Oro
The Qubit Cowboy!
(El Caballero Qubit!)
Don't Panic. Carry on.
Tim and USTC PhD student Zuen Su.

The pointer is mightier than the pen!

At the other Middle Eastern Restaurant — Shally Lally!

"It's not a REAL party until somebody starts talking about delta functions?"

LSU-USTC-NYU collaboration!
More traditional fold dancing to the music of Shakira.
(The hips may lie?)
A boy named Su!
Chenglong is happy to be back in his home country!

"No! No! No! I'm NOT marrying the HACKER!" --- Eric Song