This study reports the first experimental demonstration of SU(2) valley coherence generation and detection in monolayer WSe₂. Using optical techniques, the researchers show that valley excitons can be coherently manipulated, similar to spin states in quantum technologies. They establish circularly polarized optical selection rules for addressing individual valley excitons and trions in monolayer WSe₂. Linearly polarized luminescence is observed, indicating coherence between valley excitons, as excitons in a single valley emit circularly polarized photons. In contrast, trion photoluminescence is not linearly polarized, consistent with the expectation that emitted photon polarization is entangled with valley pseudospin. The ability to address coherence, in addition to valley polarization, adds a critical dimension to the quantum manipulation of valley index necessary for coherent valleytronics. Monolayer transition metal dichalcogenides (TMDCs) are two-dimensional semiconductors with a direct band gap in the visible range. They have energy-degenerate valleys at the corners of the hexagonal Brillouin zone. Excitons and trions form in these materials, with excitons formed by bound electron-hole pairs and trions by excess carriers. In monolayer TMDCs, electrons and holes are confined to the ±K valleys, leading to valley excitons and trions at energy-degenerate points in momentum space. The study investigates the generation and readout of excitonic intervalley quantum coherence in monolayer WSe₂ devices via polarization resolved photoluminescence (PL) spectroscopy. Monolayer WSe₂ is obtained through mechanical exfoliation of synthetic WSe₂ crystals onto SiO₂ substrates. The sample is studied at 30 K with an excitation energy of 1.88 eV and spot size of 1.5 μm. The PL spectra show two pronounced excitonic emission features at 1.71 and 1.74 eV, identified as A excitons. The PL intensity, binding energy, and polarization dependence show that X' behaves the same as X⁻ and likely arises from the fine structure of X⁻. The study also investigates valley exciton polarization. The PL of X⁺, X⁰, X⁻, and X' are all highly circularly polarized, demonstrating that valley optical selection rules derived from the single particle picture are inherited by both neutral and charged excitonic states. The ground state configurations for valley excitons and trions and their optical selection rules are schematically shown. The observed polarization is independent of crystal orientation, indicating a unique origin of linear polarization in monolayer WSe₂. The most significant finding is that for linearly polarized light excitation, X⁰ emission is also highly linearly polarized, while trion PL is not. This is attributed to the generation of excitonic quantum coherence between opposite valleys by linearly polarized light.This study reports the first experimental demonstration of SU(2) valley coherence generation and detection in monolayer WSe₂. Using optical techniques, the researchers show that valley excitons can be coherently manipulated, similar to spin states in quantum technologies. They establish circularly polarized optical selection rules for addressing individual valley excitons and trions in monolayer WSe₂. Linearly polarized luminescence is observed, indicating coherence between valley excitons, as excitons in a single valley emit circularly polarized photons. In contrast, trion photoluminescence is not linearly polarized, consistent with the expectation that emitted photon polarization is entangled with valley pseudospin. The ability to address coherence, in addition to valley polarization, adds a critical dimension to the quantum manipulation of valley index necessary for coherent valleytronics. Monolayer transition metal dichalcogenides (TMDCs) are two-dimensional semiconductors with a direct band gap in the visible range. They have energy-degenerate valleys at the corners of the hexagonal Brillouin zone. Excitons and trions form in these materials, with excitons formed by bound electron-hole pairs and trions by excess carriers. In monolayer TMDCs, electrons and holes are confined to the ±K valleys, leading to valley excitons and trions at energy-degenerate points in momentum space. The study investigates the generation and readout of excitonic intervalley quantum coherence in monolayer WSe₂ devices via polarization resolved photoluminescence (PL) spectroscopy. Monolayer WSe₂ is obtained through mechanical exfoliation of synthetic WSe₂ crystals onto SiO₂ substrates. The sample is studied at 30 K with an excitation energy of 1.88 eV and spot size of 1.5 μm. The PL spectra show two pronounced excitonic emission features at 1.71 and 1.74 eV, identified as A excitons. The PL intensity, binding energy, and polarization dependence show that X' behaves the same as X⁻ and likely arises from the fine structure of X⁻. The study also investigates valley exciton polarization. The PL of X⁺, X⁰, X⁻, and X' are all highly circularly polarized, demonstrating that valley optical selection rules derived from the single particle picture are inherited by both neutral and charged excitonic states. The ground state configurations for valley excitons and trions and their optical selection rules are schematically shown. The observed polarization is independent of crystal orientation, indicating a unique origin of linear polarization in monolayer WSe₂. The most significant finding is that for linearly polarized light excitation, X⁰ emission is also highly linearly polarized, while trion PL is not. This is attributed to the generation of excitonic quantum coherence between opposite valleys by linearly polarized light.