{"product_id":"wignera-wigners-friend-physics-t-shirt","title":"Wignera – Wigner's Friend Physics T-Shirt","description":"\u003cp\u003eWignera's friend measured the qubit inside the lab. To Wignera, outside, the friend is still in superposition. Who is right?\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eA friend measures a qubit inside a sealed lab. Treating the whole lab with quantum mechanics, an outside observer assigns an entangled state of qubit and friend, while the friend has seen a definite result. Recent no-go theorems show that some reasonable assumptions about observers cannot all hold together.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003e|Ψ⟩ = (|0⟩|F₀⟩ + |1⟩|F₁⟩)\/√2\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e|0⟩, |1⟩: qubit states\u003c\/li\u003e\n\u003cli\u003e|F₀⟩, |F₁⟩: friend having seen 0 or 1\u003c\/li\u003e\n\u003cli\u003e|Ψ⟩: joint state of qubit and friend\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eEugene Wigner posed it in 1961; Frauchiger and Renner sharpened it in 2018, and Bong et al. (2020) proved a stronger no-go theorem with a proof-of-principle photon experiment.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e Which assumption fails is still debated, and neither observer is simply \"right\". In the 2020 experiment a photon's path stood in for the observer.\u003c\/p\u003e\u003ch3\u003eOn the shirt\u003c\/h3\u003e\u003cp\u003eFront: Wignera, the pixel-art character, with the title. Back: the entangled lab state, the two viewpoints, the no-go theorems and the 1961, 2018 and 2020 sources. Printed on a unisex tee.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"S \/ White","offer_id":50936699682919,"sku":"70113374985765105838","price":29.99,"currency_code":"USD","in_stock":true},{"title":"S \/ Black","offer_id":50936699715687,"sku":"15063698798526829346","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ White","offer_id":50936699748455,"sku":"20591619646180480927","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ Black","offer_id":50936699781223,"sku":"10683069294061549142","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ White","offer_id":50936699813991,"sku":"75256266432241388750","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ Black","offer_id":50936699846759,"sku":"10837869111240950390","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ White","offer_id":50936699879527,"sku":"25101596417578212733","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ Black","offer_id":50936699912295,"sku":"21102156111869375775","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ White","offer_id":50936699945063,"sku":"11653202418247662806","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ Black","offer_id":50936699977831,"sku":"14405955009294675231","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ White","offer_id":50936700010599,"sku":"16129013550542618599","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ Black","offer_id":50936700043367,"sku":"13167876774745333239","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ White","offer_id":50936700076135,"sku":"29583807537922640155","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ Black","offer_id":50936700108903,"sku":"20494385813369455489","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ White","offer_id":50936700141671,"sku":"20494611554580223674","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ Black","offer_id":50936700174439,"sku":"24979561816962521773","price":29.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/wigners-friend_front_01_white.png?v=1793595960","url":"https:\/\/pixelatedphysics.com\/pl\/products\/wignera-wigners-friend-physics-t-shirt","provider":"Pixelated Physics","version":"1.0","type":"link"}