Laser-plasma accelerators (LPAs) are capable of sustaining accelerating fields of 1-100 GeV/m, 10-1000 times that of conventional RF technology, and the highest fields produced by any of the widely researched advanced accelerator concepts. Furthermore, LPAs intrinsically produce short particle bunches, 100-1000 times shorter than that of conventional RF technology, which leads to reductions in beamstrahlung and savings in overall power consumption. Furthermore, they enable novel energy recovering methods that can reduce power consumption and improve the luminosity per unit energy consumption for linear colliders. These properties make LPAs a promising candidate as drivers for a more compact, less expensive high-energy collider by providing multi-TeV polarized leptons in a relatively short distance ∼1 km. Collider concepts are discussed up to the 15 TeV range. A future RF-based linear collider facility could be re-purposed to delivery higher energies with LPA technology thereby extending physics reach while saving on construction costs.Previous reports have made strong recommendations for a vigorous program on LPA R&D and applications, including the previous P5 and subcommittee reports, the European Strategy and Laboratory Directors Group reports, and several others. Numerous significant results have been obtained since the last P5 report, including the production of high quality electron bunches at 8 GeV from a single stage, the staging of two LPA modules, novel injection techniques for ultra-high beam brightness, investigation of processes that stabilize beam break up, new concepts for positron acceleration, and new technologies for high-average-power, high-efficiency lasers. In addition to the long term goal of a high energy collider, LPAs can provide compact sources of particles and photons for a wide variety of near-term applications in science, medicine, and industry.Research on LPAs has exploded in recent years, driven in part by the extremely rapid advances made in high-power lasers based on the 2018 Nobel Prize winning technique of chirped-pulse amplification. Numerous high-power laser facilities have sprung up worldwide, particularly in Europe and Asia. Consequently, about 800-1000 research papers are published annually on LPAs. Since much of this research is overseas, it is critical that the U.S. make strong investments in LPAs to ensure global leadership.The LPA community proposes the following recommendations to the Snowmass conveners:1. Vigorous research on LPAs, including experimental, theoretical, and computational components, continue as part of the General Accelerator R&D program to make rapid progress along the LPA R&D roadmap towards an eventual high energy collider, develop intermediate applications, and ensure international competitiveness.2. Enhance R&D on laser drivers to develop the efficient, high repetition rate, high average power laser technology that will power LPA colliders.3. Near-term LPA capability extensions should be carried out, such as enhancing existing facilities in laser pe...

The Petawatt (PW) laser facility of the Berkeley Lab Laser Accelerator (BELLA) Center has recently commissioned its second laser pulse transport line. This new beamline can be operated in parallel with the first beamline and enables strong-field quantum electrodynamics (SF-QED) experiments at BELLA. In this paper, we present an overview of the upgraded BELLA PW facility with a SF-QED experimental layout in which intense laser pulses collide with GeV-class laserwakefield-accelerated electron beams. We present simulation results showing that experiments will allow the study of laser-particle interactions from the classical to the SF-QED regime with a nonlinear quantum parameter of up to χ ∼2. In addition, we show that experiments will enable the study and production of GeV-class, mrad-divergence positron beams via the Breit-Wheeler process.