Add pomegranate juice and 4 rosemary sprigs to a saucepan and boil gently. Add sugar and cook until sugar dissolves. Simmer 10-12 minutes, until juice reduces by 2/3. Remove from heat and strain out rosemary. Let cool.
Divide syrup between four wine glasses. Add one teaspoon (five milliliters) of lemon juice to each glass. Top with 1/2 cup (120 milliliters) soda, 1/2 cup (120 milliliters) tonic water. Garnish with a spoonful of pomegranate seeds and one sprig of rosemary per glass.
For an alcoholic version, replace club soda and tonic water with prosecco.