Abstract Organic high electron spin states, such as quintet state, can be used as multiple quantum bits for implementing quantum information. However, the practical quintet state via singlet fission is generally observed in strict conditions. Achieving long‐term quantum coherence of quintets at room temperature is still challenging. Here, quantum coherence in electron quintet states up to 505 ns at room temperature is observed, enabling quantum operations up to 54 times. Detailed investigations show that two Rabi oscillations from the multiple levels of the quintet are detectable at room temperature, with frequencies of 1.69 ± 0.01 and 1.39 ± 0.01 times of that of triplet states, respectively. More importantly, this quintet derived from singlet fission process can be realized via a simple co‐melting technology with amorphous form of 6,13‐bis(triisopropylsilylethynyl)pentacene dopped 1,3,5‐tri(1‐naphthyl)benzene (TIPS‐Pn:TNB). The organic TNB host with light elements is helpful for achieving long decoherence time. This study not only proves a simple method for preparing controllable quintet state at room temperature, but also emphasizes the opportunities of organic high electron spin states in quantum information science for working at low‐cost and friendly condition.
Abstract Organic high electron spin states, such as quintet state, can be used as multiple quantum bits for implementing quantum information. However, the practical quintet state via singlet fission is generally observed in strict conditions. Achieving long‐term quantum coherence of quintets at room temperature is still challenging. Here, quantum coherence in electron quintet states up to 505 ns at room temperature is observed, enabling quantum operations up to 54 times. Detailed investigations show that two Rabi oscillations from the multiple levels of the quintet are detectable at room temperature, with frequencies of 1.69 ± 0.01 and 1.39 ± 0.01 times of that of triplet states, respectively. More importantly, this quintet derived from singlet fission process can be realized via a simple co‐melting technology with amorphous form of 6,13‐bis(triisopropylsilylethynyl)pentacene dopped 1,3,5‐tri(1‐naphthyl)benzene (TIPS‐Pn:TNB). The organic TNB host with light elements is helpful for achieving long decoherence time. This study not only proves a simple method for preparing controllable quintet state at room temperature, but also emphasizes the opportunities of organic high electron spin states in quantum information science for working at low‐cost and friendly condition.
Multiexciton quintet states, 5 (TT), photogenerated in organic semiconductors using singlet fission (SF), consist of four quantum entangled spins, promising to enable new applications in quantum information science. However, the factors that determine the spin coherence of these states remain underexplored. Here, we engineer the packing of tetracene molecules within single crystals of 5,12-bis(tricyclohexylsilylethynyl)tetracene (TCHS–tetracene) to demonstrate a 5 (TT) state that exhibits promising spin qubit properties, including a coherence time, T 2, = 3 μs at 10 K, a population lifetime, T pop, = 130 μs at 5 K, and stability even at room temperature. The single-crystal platform also enables global alignment of the spins and, consequently, individual addressability of the spin-sublevel transitions. Decoherence mechanisms, including exciton diffusion, electronic dipolar coupling, and nuclear hyperfine interactions, are elucidated, providing design principles for increasing T 2 and the operational temperature of 5 (TT). By dynamically decoupling 5 (TT) from the surrounding spin bath, T 2 = 10 μs is achieved. These results demonstrate the viability of harnessing singlet fission to initiate multiple electron spins in a well-defined quantum state for next-generation molecular-based quantum technologies.
Quantum-to-quantum transduction is the coherent exchange of information between quantum systems, which is an essential element of quantum information science (QIS). Molecular architectures provide unmatched flexibility for tailoring the properties that are critical to quantum transduction, and molecular synthesis affords the opportunity to build novel molecular materials from the bottom-up. Singlet fission (SF) in organic chromophore solids provides a potential means of executing photon-to-spin quantum transduction because absorption of a single photon results in formation of four entangled spins that constitute a triplet pair state (TT). We have demonstrated that SF in single crystals of 5,12-bis(tricyclohexylsilylethynyl)-tetracene (TCHS-tetracene) produces a long-lived quintet state 5 (TT) that provides a promising new route to multiqubit systems for QIS. Here, we investigate the interaction of classical and entangled photons with TCHS-tetracene as well as the related TIPS-tetracene and tetracene to assess the molecular properties required for quantum transduction. From the classical two-photon absorption (TPA) experiment, we observed that TCHS-tetracene and TIPS-tetracene have a higher TPA cross-section than tetracene. The entangled TPA cross-sections of TCHS-tetracene and TIPS-tetracene (6.914 × 10 –19 and 5.057 × 10 –19 cm 2 /molecule, respectively) are about an order of magnitude larger than that of tetracene (5.146 × 10 –20 cm 2 /molecule), making TCHS-tetracene and TIPS-tetracene excellent candidates for demonstrating photon-to-spin transduction using SF. We also observed a longer coherence time for the TCHS-tetracene in comparison to the tetracene molecular systems investigated, which suggests its suitability for possible QIS applications.
Quantum electronics operating in the microwave domain are burgeoning and becoming essential building blocks of quantum computers, sensors, and communication devices. However, the field of microwave quantum electronics has long been dominated by the need for cryogenic conditions to maintain delicate quantum characteristics. Here, a solid-state hybrid system, constituted by a photo-excited pentacene triplet spin ensemble coupled to a dielectric resonator, is reported for the first time capable of both coherent microwave quantum amplification and oscillation at X band via the masing process at room temperature. By incorporating external driving and active dissipation control into the hybrid system, efficient tuning of the maser emission characteristics at ≈9.4 GHz is achieved, which is key to optimizing the performance of the maser device. The work not only pushes the boundaries of the operating frequency and functionality of the existing pentacene masers but also demonstrates a universal route for controlling the masing process at room temperature, highlighting opportunities for optimizing emerging solid-state masers for quantum information processing and communication.
One of the main challenges facing quantum information science (QIS) is the development of robust qubits that can be operated under ambient conditions. Current state-of-the-art anionic nitrogen-vacancy center (NV – ) defect qubits are robust enough to be operated at room temperature but lack scalability and tunability. These are areas where molecular qubits excel, although, in contrast, they typically suffer from poor air stability and fast decoherence at elevated temperatures and in magnetically noisy environments. Organic-based systems offer possible advantages to this end, although examples retaining room temperature coherence are still rare. Furthermore, most organic-based systems lack optical transitions similar to NV – centers that could allow for optical initialization and readout. Here we report two new organic-based qubit candidates that demonstrate room temperature coherence in nuclear and electron spin-rich environments. These qubits luminesce far into the near-infrared (NIR, 700–1700 nm) and telecom (∼1260–1625 nm) regions, ideal for biological sensing and communications applications, respectively.
Molecular systems with optically addressable electron spins are emerging as versatile quantum sensing platforms, offering tunable qubit properties and molecular-scale spatial control. Owing to their longer lifetimes, coupled nuclear spins provide an attractive resource for enhancing sensing performance. For molecular spin systems, the ability to initialise, coherently control and readout nuclear spins at room temperature is crucial for realising such benefits. Here, we present the first optical detection of nuclear magnetic resonance and coherent nuclear spin control with a molecular system at room temperature. Specifically, we demonstrate optically detected Rabi oscillations of 14N nuclear spins in the photoexcited triplet state of the organic chromophore 6,13-diazapentacene. The strong hyperfine coupling between the electronic spin and 14N nuclei enhances the nuclear Rabi frequency, enabling fast coherent nuclear-spin rotations. This work lays the foundation for leveraging nuclear spins as memories for enhanced molecular-based quantum sensing.
Abstract Crystal defects in solid‐state spintronic materials play a crucial role in altering the optical properties of their hosts, enabling widespread applications in the field of quantum information processing. While the majority of the leading platforms are inorganic, they come with limitations such as the challenging material preparations and insufficient amount of active spins. Here, pentacene‐doped p‐terphenyl (Pc:Ptp), an organic spintronic material with easy preparations and tailorable functionalities normally used for microwave quantum electronics, is demonstrated for the first time its ability of self‐cavity laser emission at room temperature. The laser emission is characterized by strong polarization and anisotropy, attributed to the unique packing of the doped molecules (i.e., active spins) within the crystal. The optical coherence is found to be a figure of merit to distinguish the processes of the amplified spontaneous emission (ASE) and lasing in Pc:Ptp. This work highlights the potential of Pc:Ptp as a compact and efficient platform for light‐matter interactions, offering significant promise for enhancing the performance of solid‐state quantum devices based on the organic spintronic material.