Where I couldn’t bid goodbye

I still don’t have the courage to buy Teachers’ Day cards.

It was 11^{th of} August 2018. I was sitting in a tea shop and drinking a cup of black tea with a friend. We were waiting for the bus to go to the city. My friend, he does not talk much in the mornings. He is either lost in thoughts or browsing through social media. I was drowsy from the medicines that I took the previous night and was staring blankly at the rows of rubber trees opposite to the tea shop. My phone beeped with a message notification.

“Our KP passed away.”

I read it, closed the app, and turned off the phone. I began staring blankly at the trees again.

“Not KP, no,” I told myself in disbelief. Last time I went to visit KP, he was alright, and it was just two weeks ago that I spoke to him over the phone. I checked the message again, hoping that it was a moment of horrific hallucination. But it was not.

My heart was racing, and I was sweating. I touched my friend’s hand and he looked at me.

“What is the matter, why are you pale?”

“Sir is no more.”

My head was reeling, and I felt that my body was growing heavy. I could not get words out of my mouth. My mind was muffled with thoughts, but nothing was quite clear. I had flashes of him taking classes, holding discussions in his cabin, talking about life and science.

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Porsezian or KP as we fondly called him was my professor at Pondicherry University. I met him first after a class by him on Mathematical Physics. As I entered his cabin to clarify a doubt, he asked me if I wanted the answer or a discussion. A discussion, I said and that was the beginning of an incredible mentorship.

One day, during my second year, he called me and asked what I wanted to do after masters.

“Ph.D. Theoretical nonlinear optics.”

“Good. So you don’t like experiments.”

That evening, he gave me a paper on the nature of nonlinear optics in negative index materials. I did not understand a word, but he asked me to reproduce the results from that paper. For the next ten months, I would sit in his cabin after class hours and discuss the paper. Never have I gotten an answer from him. He would drop clues and make me struggle to come up with an answer. Not just that, for every result out there, he would ask me to design an experiment and I hated that. But it was not long before my aversion for experiments numbed. I grew fond of designing experiments.

On the day I graduated, he told me that a real physicist is someone who appreciates equations and experiments alike. They are just two different ways on our quest to understand nature. Little did I know on the day he gave me the research article that I would end up being a Ph.D. student in experimental nonlinear optics.

That was just one of the several ways by which I was influenced by him. I was in touch with him even after my graduation. He knew my ups and downs.

It was not just Physics that I discussed with him. He talked to me about life and pointed out the biggest fear that I had been holding in me for years. Ever since I was a kid, my sole aim in life was to prove the world that I could achieve, and I am worthy. I had not paid attention to my health or my wishes. I did not trust people. I built a wall around me and guarded it day and night. I was revengeful. But it all changed with him.

I never told him that for the first time, I saw, a father figure in someone. Deep inside all my thoughts about my future and dreams, he was there.

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My friend asked if we should return to the hostel, I was not sure. What would I do there? The Nonlinear Optics textbook that he used to borrow from me was right on the table. I just wanted to cry but I was numb. I called my mom who by then had already got the news. I could not even cry to her. I just felt empty. That’s what the death of someone you look up to feels like. His role in my life came to a sudden stop that I had no way of responding to. I still have not responded to it. I am still numb. I am still recovering. Is there a way to fill this void? I do not know.

 

Spinning our way into the world of atoms

By Siva Shakthi and Vimal Simha, Research Matters.

In most scientific experiments, noise, consisting of random fluctuations that interfere with the measurement one is trying to make, is often a source of nuisance and anguish. However, in some experiments, scientists actually set out to probe the pattern of noise and draw useful inferences from it. For example, in 1928, scientists used random voltage fluctuations in a conductor to measure its resistance to electric current. Spatial and temporal variations are common in physical systems, and accurately measuring them can help us better understand the internal structure and other characteristics of such systems.

In a recent study, researchers at the Raman Research Institute, Bengaluru, have used a technique known as spin noise spectroscopy to probe the atomic, magnetic and sub-atomic properties of rubidium vapour. The study, published in the journal Optics Express, demonstrates that spin noise spectroscopy is a practical, non-invasive technique to study the atomic properties of many physical systems. It performs better than hitherto used methods to study the atomic properties of an element in detail.

Spin noise spectroscopy is a technique to probe physical systems using random spin fluctuations of the electrons. Like other subatomic particles, electrons have a charge and a mass, and another fundamental property known as spin. Experiments have shown that electrons behave as if they are spinning about an axis similar to a spinning top. However, unlike the spinning top, the spin of an electron appears to be an intrinsic property, and not caused by anything physically rotating within it.

There are two types of electron spin—spin-up and spin-down, roughly corresponding to anti-clockwise and clockwise rotation. In any given material, on average, there are equal numbers of spin-up and spin-down electrons. However, there can be fluctuations in the spin properties, and a detailed map of such changes could tell us more about the intrinsic properties of the material.

In the current study, the researchers used a laser beam to probe a cell containing vapours of rubidium-87, an isotope of rubidium. Like all light, the laser beam consists of oscillating electric and magnetic fields. The researchers subjected the rubidium atoms to a uniform magnetic field perpendicular to the direction of the probe beam. They then analysed the transmitted laser beam to decipher the properties of the element.

When the applied magnetic field was low, the researchers obtained a noise spectrum, caused by random spin fluctuations of the electrons. They observed two distinct peaks at two different frequencies of the transmitted light, indicating spin fluctuations of two different substances in the sample. It was because the sample, which mostly contained rubidium-87, also had trace quantities of rubidium-85, another isotope of rubidium. Traditional spectroscopy, which differentiates two substances based on the wavelengths of light they absorb, would not have revealed the presence of rubidium-85, because there is not enough of it to produce an observable absorption line.

As the strength of the magnetic field is increased, the researchers observed that the peaks in the transmitted spin noise spectrum broadened. From this, they say that a precise measurement of the magnetic field could be established.

“Even at room temperature the spin noise signal is reasonably narrow in frequency, making it a useful tool for precise detection of the external magnetic field,” say the researchers.

At low temperatures, the precision is expected to be far better since cold atoms collide less often, producing fewer effects that interfere with the measurement.

The researchers also extended the spin noise spectroscopy technique to explore what happens under non-equilibrium conditions, where the balance between the spin-up and spin-down states, was disturbed. They used a control laser beam to obtain different spin populations of electrons and then demonstrated that these differences are reflected in the noise spectra they get.

The researchers say that the technique can also be used to probe other properties such as the boundary between different phases of matter by mapping the spins of atoms in the substance.

“The origin of magnetism of matter can also be better understood using this technique”, say the researchers. “In a nutshell, this technique can be used to explore several open questions in quantum magnetism,” they conclude.

The stalwart slayer

Woman, ew, hair on your legs, I see.
No liquid sunshine, I am not.
Can’t purge the repugnance you see.
Woman, ew, fat on your thighs, I see.
No meagre warmth, I am not.
Can’t melt away the blimp you see.
Woman, ew, sagging bosoms, I see.
No pole, I am not.
Can’t hold them uptight, you see?
Woman, ew, no grace I see.
No breeze, I am not.
To waft through free.
Woman, ew, raise not your voice.
No blind, I am not.
To your depravity.
Woman, ew, workplace is ours, you see?
Inept, I am not.
To your bigotry.
No liquid sunshine, I am.
To drizzle and pet.
But a stalwart slayer,
For meaningless absurdity.