Quantum Technologies and Sensing Questions & Answers

What is quantum technology? What is the role of photonics in quantum technology?
What is the advantage of using photonics in quantum systems?
What role does photonics play in quantum sensing?
Are there other resources for learning more about quantum sensing?

What is quantum technology? What is the role of photonics in quantum technology?

Quantum technology is an emerging field that aims to manipulate quantum phenomena, such as superposition and entanglement, to engineer systems that harness and exploit these laws to process and secure information. The pillars of quantum technology often include, but are not limited to, quantum computation, quantum communication, and quantum sensing. Below I highlighted what role photons play in each pillar.

Quantum computing & simulation: Photonics enables the ability to confine qubits (e.g., atoms) in arrays and detect qubit states (0 or 1) through low light fluorescence from ions and atoms.
Quantum communication: The photon acts as a secure carrier of information especially over long distances, and has the ability to notify users immediately when an eavesdropper is listening.
Quantum meteorology & sensing: Materials such as nitrogen vacancy (NV) can act as high-sensitivity probes for strain and magnetic and electric fields through fluorescence.
Fundamental research (ex: quantum optics): Photons can characterize quantum phenomenon such as entanglement through detection and imaging.

**Quantum technologies with photons**
Quantum Computation & Simulation	Quantum Communication	Quantum Meteorology & Sensing	Fundamental Research
Superconducting* Trapped ions Neutral atoms Photonic Nitrogen vacancy	Quantum Random Number Generators (QRNG) Continuous variable (CV) – QKD Discrete variable (DV) - QKD [with no entanglement] Discrete variable (DV) - QKD [entanglement-based] High-dimensional – QKD Quantum repeaters Quantum memories/buffers	Medical sensing & imaging Quantum sensors for GPS free navigation Gravimeters Atomic clocks	Quantum optics Quantum imaging Quantum biology Single photon sources/ Entangled photon sources

*To scale superconducting qubits some photonic link ideas have been demonstrated.
Not an exhaustive list

What is the advantage of using photonics in quantum systems?

One advantage is that photons are easy to manipulate using standard components like phase shifters and beam splitters. Networking of quantum computer hardware like photonic chips or ion-trapped modules is slightly easier when utilizing photonics since there is no need for transducers. Photonic components are embedded in the hardware, so it is easier to transport quantum information from one chip to another via optical fibers. One of the scaling architectures currently being investigated for trapped ions, a quantum computing qubit modality that uses photonics, is a network of ion-trapped modules which are linked via optical fibers [1]. The ability to network and transport information is vital to overcome challenges like scaling.

For quantum communication that requires sending information over long distances like a quantum network, the photon has demonstrated itself as a reliable carrier of information as it has been tried and tested in other fields such as optical fiber networks.

What role does photonics play in quantum sensing?

Quantum sensing exploits quantum systems’ extreme sensitivity to environmental factors to measure physical properties with more precision [2].

Nitrogen vacancy

One of the areas of active research in quantum sensing involves nitrogen vacancies (NV). NVs can act as high-sensitivity probes of magnetic fields, electric fields, charge, voltage, and pressure. NVs have attractive properties that include long coherence times on the order of milliseconds at room temperature.

Examples of photonic components used in NV:

Modulators (LCOS-SLM): An example usage is to generate multi-focal beam arrays to enable faster and parallel laser writing of color centers [3]
Si photodiode: Monitoring laser power or measuring higher light intensities of the NV fluorescence [4] [5]
MPPC/SPPC (SiPM/SPAD): Detecting low light NV fluorescence [6]
Camera: Imaging and detecting weak fluorescence from NV [7]

Diamond NV center

Figure 1. Experimental setup using nitrogen vacancy

Are there other resources for learning more about quantum sensing?

Check out some of our past webinars.

Quantum sensing in atomic and solid-state systems, presented by Prof. Jennifer Choy, Ph.D., of the University of Wisconsin-Madison
Quantum sensing: Probing biological systems in a new light, presented by Prof. Peter Maurer from University of Chicago, Pritzker School of Molecular Engineering

Another resource is WIRED Magazine's video on quantum sensing, presented by Prof. Chandrasekhar Ramanathan of Dartmouth College.

References

[1] Brown, K., Kim, J. & Monroe, C. Co-designing a scalable quantum computer with trapped atomic ions. npj Quantum Inf 2, 16034 (2016). https://doi.org/10.1038/npjqi.2016.34.
[2] T. Hausken et al., “OIDA Quantum Photonics Roadmap,” OSA Industry Development Associates Report, 2020.

[3] M. Barbiero, S. Castelletto, and M. Gu, “Multi-focal laser fabrication of nitrogen vacancy centres in a bulk diamond,” OSA Continuum 3(12), 3416–3423 (2020).

[4] F. M. Stürner et al., “Integrated and portable magnetometer based on nitrogen-vacancy ensembles in diamond,” Adv. Quantum Technol., vol. 4, no. 4, Apr. 2021, Art. no. 2000111.

[5] Jeong Hyun Shim, Seong-Joo Lee, Santosh Ghimire, Ju Il Hwang, Kwang-Geol Lee, Kiwoong Kim, Matthew J. Turner, Connor A. Hart, Ronald L. Walsworth, and Sangwon Oh. Multiplexed sensing of magnetic field and temperature in real time using a nitrogen vacancy spin ensemble in diamond. Phys. Rev. Applied, 17(1):014009, January 2022.

[6] Chen Y, Balasubramanian P, Cai Y, et al. Quantum calibration of multi-pixel photon counter and its application in high-sensitivity magnetometry with NV center ensemble. IEEE J Sel Top Quantum Electron. 2020;26(3):1-7. https://doi.org/10.1109/JSTQE.2020.2991432.

[7] Basso L., Sacco M., Bazzanella N., Cazzanelli M., Barge A., Orlandi M., Bifone A., Miotello A. Laser-Synthesis of NV-Centers-Enriched Nanodiamonds: Effect of Different Nitrogen Sources. Micromachines. 2020;11:579. doi: 10.3390/mi11060579

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Meet the engineer

Klea Dhimitri is an applications engineer out of Hamamatsu’s office in Bridgewater, NJ, where she focuses on product offerings for emerging quantum technology applications that utilize photonics. Her expertise includes photodetectors such as photomultiplier tubes (PMTs), SPPC (SPAD), MPPC (SiPM), photodiodes, and avalanche photodiodes (APD), as well as their role in quantum applications. Klea leads Hamamatsu's efforts in bringing our R&D from Japan together with researchers and early adopters in North America to provide a range of photonic solutions, from detectors to light modulators to cameras, for the current and future quantum landscape. She also manages Hamamatsu Corporation’s engagement and activities in North American quantum hubs like Chicago Quantum Exchange (CQE). In her spare time, she enjoys endurance-based sports such as running and biking, and is currently training to run her first marathon in the fall.

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