As soon as my QR code is opened in Adobe Photoshop, the size is reduced. Is there any way to maintain the size and quality of the image so that the quality is not compromised. It becomes impossible to scan once I resize it.
Don't open it in Photoshop. Place it.
Go to Preferences > General, then uncheck "Resize Image During Place." When you place the QR code file, it will maintain its dimensions, and will be a Smart Object.