By Ryan F. Mandelbaum, Senior Technical Writer, Qiskit
Qiskit events draw students, researchers, and educators from around the world — but according to our data, interest is spiking in India, both in how users are engaging with the Qiskit open source community and in how often they’re running IBM Quantum hardware.
Scientists in India have already started to undertake large-scale quantum projects. Three years ago, researchers began the country’s first satellite-based quantum communication experiment — the Quantum Experiments using Satellite Technology, or QuEST project. Another team has been building an advanced new quantum computer. And earlier this year, India gave quantum technology a 80 billion rupee ($1.07 billion) boost as part of its National Mission on Quantum Technologies and Applications, coordinating stakeholders from across industry, research, and government to spur development in quantum computing, cryptography, communications, and materials science. These efforts are set to have a global impact, while a quantum community is coalescing around newly available opportunities in the field.
“It’s a great time to be doing quantum physics because the government is serious about it, the people are serious about it, and we’re all excited about what this technology can do for India,” said Rishab Chatterjee, a graduate student from the Raman Research Institute in Bangalore, India.
An Advanced New QKD Simulator
A pioneering team led by Dr. Urbasi Sinha at the Raman Research Institute in Bangalore is poised to make a global impact when it comes to quantum key distribution (QKD). The researchers couldn’t find a public domain simulation software that took into account realistic imperfections of an experimental setup— so they developed a toolkit themselves and named it qkdSim. The team based primarily at the Raman Research Institute in Bangalore, India went on to successfully simulate an experimental setup of a QKD protocol and verify it with an actual demonstration of the protocol in free space. The experiment is a milestone for India as one of the country’s first published free-space quantum key distribution experiments, and a foundational experiment as the country grows its QKD capabilities.
“QKD is already being used and deployed in other countries, but not as much so in India,” said study author and RRI professor Urbasi Sinha. “Now that QKD is entering the commercial domain, such a simulation toolkit is of primary importance, not just here, but everywhere in the world — if you can simulate the whole system with almost every error you can think of, then you can ensure your resources won’t go to waste. Now we’ll be able to spend our money more wisely, and also have more confidence plus a benchmark for future QKD experiments.”
Quantum key distribution is a form of cryptography where the laws of quantum mechanics create a system such that it’s clear when someone is eavesdropping. There are plenty of other QKD simulators for educational and theoretical purposes, but few that actually take experimental components into account. Sinha and her team realized that as QKD matures, scientists and businesses will want to predict experimental results, including the errors, in order to build cheaper cryptography systems. Such a simulation must move beyond making theoretical predictions and incorporate how experimental components might alter important metrics like how quickly the key is generated or the error rate. QkdSim takes experimental parameters as its inputs, such as which QKD protocol to use, the experimental setup and components, the physical processes involved, and how long the protocol will run for.
The team carried out and simulated the B92 protocol, devised by IBM’s Charles Bennett in 1992, which relies on Heisenberg’s Uncertainty principle to generate quantum keys. In quantum systems, measuring in one basis randomizes the measurement in an orthogonal basis, as with a qubit’s 0/1 and +/– bases or a photon’s horizontal/vertical and ±45 degree bases. For this protocol, Alice sends a random sequence of either vertically or +45 degree-polarized photons, which represent 0 and 1 respectively, and then Bob randomly chooses whether he’d like to measure those photons in the horizontal-vertical or the ±45 degree basis. If Alice sends a vertically polarized photon and Bob measures in the horizontal/vertical basis, then he’ll always observe a vertically polarized photon, but if he measures in the ±45 degree basis, then he’ll randomly observe a + or –45 degree-polarized photon. The converse occurs if Alice sends a +45 degree-polarized photon, with Bob either correctly measuring the +45 degree-polarized photon or incorrectly measuring horizontally and vertically polarized photons at random. Whenever Bob uses the wrong basis and measures a value that Alice didn’t send, he knows for sure that the photon was sent in the other basis, and therefore knows its exact value since Alice only sent vertical and +45 degree-polarized photons. Bob publicly announces which photons were horizontally or –45 degree-polarized without announcing how he measured them, and then both Alice and Bob discard everything except the known photons. If the measured error is below a certain threshold, then the two can use the resulting bit string to send encrypted messages using the public and private information that the protocol generated. If the error is above the threshold, then an eavesdropper might be listening in.
The team demonstrated the protocol by sending single photons via an optical process called spontaneous parametric down-conversion, where a non-linear crystal generates a pair of low-energy photons from a high-energy pump photon. A set of filters removes all of the beam photons except for the generated pair, which then pass through a beam splitter. One photon goes to Bob, while Alice detects the other and records its time stamp; if Alice receives a horizontally polarized photon, then she knows she sent Bob a vertically polarized photon. The sent photon goes through another beam splitter that randomly selects between either the vertical and +45 degree states. Two meters away, Bob has his own beam splitter, set of optics, and a pair of detectors, which measure the incoming photons, perform the discarding step, and record timestamps. Bob only shares his timestamp data and not which detector it came from with Alice, then she returns his timestamp data discarding the events she didn’t detect herself. This generates the same key for both of them.
When the team ran the simulation given their own experimental components, run time, and the distance between Alice and Bob, the simulated results matched the experimental results almost exactly.
QkdSim is still in its first iteration of development, and will be including further non-idealities and imperfections in the subsequent versions, enabling a closer match with the experimental results. The team will also be incorporating a graphical user interface to the simulator. In the future, it may also be interesting to see if certain quantum resources required by QKD, like entanglement, could benefit from simulations on quantum hardware like IBM’s quantum computers.
Ultimately, simulators like these will be of great value given how they can reduce the development costs of QKD, said Arash Atashpendar, RDI Manager at itrust consulting not involved in the study. This is especially true in more expensive QKD implementations, like satellite-based QKD.
Keep your eyes open for an upcoming Qiskit seminar series featuring eminent professors in India, like Urbasi Sinha, talking about their groundbreaking work across the quantum space.
A Three-In-One Quantum Architecture
When Rajamani “Vijay” Vijayaraghavan started his Ph.D in the United States under pioneering quantum computing expert Michel Devoret, he knew that he wanted to return to India in order to do cutting-edge research in his home country. But India was traditionally stronger in quantum theory, and funding for larger experimental endeavors was hard to come by, he said. Vijay focused on small, interesting problems relating to quantum computing components, like, microwave electronics, or developing different ways to think about superconducting qubits.
In the past three years, his team has completely reoriented itself. “I did not anticipate that both the interest and support would accelerate to the level that it’s headed right now,” he said. The team is still looking at these interesting problems, but has now expanded its goals.
Vijay’s team is working on building a superconducting quantum computer based on “trimons,” rather than transmons. Transmon qubits, like those that form the basis of IBM’s quantum computers, consist of a circuit in superconducting wire where the electronic signal oscillates between a capacitor and a junction in the wire called a Josephson junction. The zero-point energy and the first mode represent the 0 and 1 qubit states, and the Josephson junction’s properties ensure that a different amount of energy is required to send the qubit from the 0 to 1 and from the 1 to 2 modes so it doesn’t accidentally oscillate in the higher modes during the calculation. Each trimon is instead a quantum circuit composed of four Josephson junctions and six capacitors that acts like three coupled transmons with its own system of modes in a three-qubit Hilbert space.
Trimons have some strengths and weaknesses versus transmons. Three-qubit gates are much easier to perform on trimon systems, and they present a different and potentially simpler way to implement some quantum algorithms, such as the Bernstein-Vazirani algorithm and Grover’s algorithm. At the same time, one- and two-qubit gates become more complicated on trimon systems.
As interest in quantum computing surges in India, and with support on the way from the National Mission, Vijay’s team is collaborating on projects with other groups, such as India’s Defense Research and Development Organization as well as Tata Consultancy Services, all while working to scale up their quantum device. They’re also working with IBM devices to benchmark their own trimon qubits, and hope to one day put a small quantum processor on the cloud that researchers can access via Qiskit. The main challenges in scaling up the system aren’t only the technical — it will also require attracting, training, and maintaining talent both from India and abroad, Vijay said.
Vijay pointed out that India isn’t building its quantum ecosystem on as old a foundation of experimental research as universities in the United States and Europe. But, while it might seem to some like India is “late,” there are still plenty of research breakthroughs necessary in the field. “A critical breakthrough today could change the course of the technology and happen anywhere in the world,” he said. “Why not India?”
Building a Quantum Computing Community in India
As quantum computing interest grows in India, so too does the community around it. Community is crucial for growing and maintaining such an interdisciplinary field.
“When I first got interested in quantum computing, there was a dearth of knowledge on how one could contribute to the field” said Rana Prathap Simh Mukthavaram, Co-op at IBM Quantum and Qiskit. “However, by meeting people and participating in competitions, I realized that there was a place for pretty much everyone who’s interested.”
Students, researchers, and scientists have formed clubs and organizations such as the non-profit organization IndiQ. Rahul Pratap Singh, Rana Prathap Simh Mukthavaram, Samanvay Sharma and Frederik Hardervig founded IndiQ with the help of Qiskit Advocate Junye Huang after Qiskit Camp Asia 2019. The group organizes events and meet-ups on quantum education and is now working to create awareness on quantum science and technology. IndiQ has already hosted a game jam, as well as meetups in Hyderabad, Delhi and Bangalore.
Qiskit has also hosted and will continue hosting events tailored to quantum researchers in India. On July 27, we held a meetup for professors in India to learn about Qiskit and network with one another. In early September, we’ll be hosting the Qiskit Challenge India, a two-week-long quantum machine learning challenge exclusive to India where contestants will first be provided with learning material and exercises to strengthen their quantum computing knowledge before tackling a quantum classification problem.
Quantum computing interest in India isn’t just coming from the top down — we’ve already noticed spikes in engagement on social media, plus thousands of signups in just the past few months for IBM’s Quantum Experience as well as Qiskit. We just concluded our Qiskit Global Summer School, and students from India formed the largest group of attendees from any country aside from the United States. As a result of the summer school, QGSS participants interested in continuing to build a quantum community coalesced into a Discord server now managed by IndiQ.
As interest quantum computing expands around the globe, we’re excited to see what people can do with Qiskit, and more importantly, the kinds of national and international communities that form as we build this field together.