Quantum NMR RF Sensing of Phosphorous-31 (³¹P) and Fluorine-19 (¹⁹F) Using Pentacene-Doped Organic Crystals for Precision-Threat Identification Phase II

Technical Abstract

Quantum sensing is at the forefront of the second quantum revolution, turning quantum coherence and entanglement into real-world sensing capabilities. This Phase II effort will develop a compact, pentacene based quantum RF/NMR sensing system for close contact detection of phosphorus 31 (³¹P) and fluorine 19 (¹⁹F) signatures in high consequence chemical threat compounds. Many priority hazards, including organophosphorus nerve agents, fluorinated oxidizers, and specialized energetic materials, are difficult to detect with current Army sensors because they are low volatility, encapsulated, or embedded in cluttered matrices.

Our approach uses pentacene doped p terphenyl organic crystals as a room temperature quantum sensing medium that reads out intrinsically selective ³¹P and ¹⁹F NMR signatures at low magnetic fields, providing a chemical fingerprint that is hard to spoof and directly linked to molecular structure.

Phase I established feasibility by demonstrating that pentacene doped p terphenyl is a credible, lower cost, and scalable alternative to diamond NV for quantum sensing. We grew ultra-pure Bridgman crystals at multiple dopant levels, achieved optically detected magnetic resonance (ODMR) with more than 7 percent contrast and linewidths below 8 MHz, and demonstrated complete qubit initialization and control using 532 nm excitation and a programmable microwave stack. Coherence times of  ≈ 2.5 µs and  ≈ 20 µs were extended to  ≈ 18 µs with Carr Purcell Meiboom Gill decoupling, approaching the  ceiling, and we implemented and modeled a Qdyne style quantum heterodyne protocol that down converts test RF fields into low frequency oscillations in the ODMR signal. Phase I also showed that pentacene crystals can be grown and processed at a fraction of the cost of engineered NV diamond, with a single crystal yielding up to 100 sensing disks at an estimated 15 to 20 dollars per disk.

Building on this foundation, Phase II will pursue four integrated objectives: (1) raise  and  through improved purification, growth, and surface preparation of bulk and thin film pentacene sensors; (2) mature triplet specific quantum control and dynamical decoupling (CPMG, XY4) together with Qdyne style RF/NMR protocols tuned to the 0.1 to 5 MHz band; (3) design and build a rugged, battery powered prototype that integrates the pentacene sensor, diode laser excitation, permanent magnet bias field, micro optics, RF and microwave delivery, and embedded control and signal processing in a 10 by 10 by 20 cm form factor; and (4) demonstrate application relevant detection and discrimination of ³¹P and ¹⁹F bearing threat surrogates in compact, close contact scenarios that mirror Army exploitation and forensic use cases. The resulting system will give the Army a portable, intrinsically selective quantum sensor for ³¹P and ¹⁹F detection, with clear pathways to broader dual use applications in chemical verification, logistics monitoring, and critical materials assurance.

Anticipated benefit / potential commercial applications of the research

Quantum sensing capabilities are now a focal point of competition among major world powers and are at the forefront of the second quantum revolution, as nations race to turn quantum advantage into practical systems. The proposed pentacene based quantum RF/NMR sensing system will provide the Army with a new capability for close contact identification of phosphorus and fluorine bearing threat materials in cluttered, shielded, or low volatility environments where current chemical sensors often fail. By directly measuring nuclear magnetic resonance signatures from ³¹P and ¹⁹F at or near room temperature, the sensor can distinguish hazardous organophosphorus agents, fluorinated oxidizers, and specialized energetics from benign background materials based on intrinsic nuclear properties rather than bulk physical or optical characteristics. This intrinsic specificity is expected to reduce false alarms, improve confidence in “clear/contaminate” decisions, and shorten time to actionable intelligence for CBRNE response, exploitation laboratories, and checkpoint screening teams. The pentacene platform also offers practical advantages over diamond NV sensors, including much lower material cost and more straightforward scalability, which supports deployment of multiple rugged units instead of a small number of laboratory grade instruments.

Beyond direct Army benefit, the same quantum RF/NMR engine has broad dual use potential. Close contact detection of ³¹P and ¹⁹F is relevant to verification of specialty chemicals and propellants, monitoring of precursor streams in chemical manufacturing, and quality control for batteries, polymers, and fluorinated coatings. In logistics and sustainment, compact sensors can be used to track degradation signatures in stored propellants or specialty materials, improving safety and lifecycle management. With appropriate software and automation, the Phase II prototype can be extended into a library driven, AI assisted analysis tool that matches measured RF/NMR signatures against a curated database of threat and benign compounds and reports a confidence ranked identification to the operator. This software layer will enable simplified user training and lower operator burden, which is critical for non-expert users in the field.

In the longer term, the core pentacene quantum sensing platform can be adapted to other nuclei and use cases, including low field NMR for pharmaceutical analysis, process monitoring in the chemical industry, and research tools for materials science. The same control and readout hardware, combined with different crystals or sequence settings, can also support magnetic field sensing applications relevant to infrastructure monitoring and scientific instrumentation. Taken together, these applications create a realistic path from a focused ³¹P/¹⁹F threat detection tool in Phase II to a small family of commercial quantum RF/NMR products that serve defense, security, industrial, and research markets.

key words or phrases:

quantum RF/NMR sensing, pentacene-doped p-terphenyl, room-temperature quantum sensor, ³¹P and ¹⁹F detection, chemical and nuclear threat identification, low-SWaP portable sensor, NV-diamond alternative, Army close-contact exploitation tool